Technical Part 1

8/16/2019 Technical Part 1

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1. TOOLS

1.0 Bench work and fitting

1.1 Vices: - used for holding work. Size is specified by width of Jaws and Maximum opening between the

Jaws.

* Bench ice is also !ngineer"s parallel #ice and also known as fitter"s #ice.

* $eg #ice is used by black smith for hea#y work. Suitable for hea#y hammering and cutting work.

* %ipe #ice used for holding round section tubes& pipes.

* 'and #ice is used for holding light work and for gripping ri#ets& keys& screws and

small drills etc.

* %in #ice is used for holding small diameter works such as wires and pins.

* (ool maker"s #ice useful for holding small work.

1.) Hammers + used to deli#er blows. Made from forged steel and specified by its weight.

*. Ball peen hammer is also known as !ngineer"s hammer. (his is chiefly used for chipping and ri#eting.

* ,ross peen hammer is used for bending& stretching& hammering.

Straight peen hammer used for stretching or peening etc.

* Soft hammer is also called mallet made of wood& hard rubber& lead and copper.

1.-. Chisels + are used for cutting and chipping away pieces of metal. Made of high carbon steel.

* lat chisel is used for general chipping operations.

* ,ross cut chisel is also known as cape chisel. /sed for cutting groo#es in large surface.

* 0ound nose chisel useful for cutting oil groo#es in bearings.

* iamond point chisel used for cutting #+groo#e

1.2 iles iles are used to cut& trim or finish a 3ob of metal or wood. 4t is specified by its length and made from

high carbon steel or tungsten steel. 5 file can remo#es the metal only on the forward stroke. iles are classified

into four types.

6a7 8n the basis of length 6b7 on the basis of shape

6c7 8n the basis of grade. 6d7 8n the basis+of cut

* 0ound and half round files are used for round cutting& filing cur#ed surfaces and enlarging holes.

* 9nife edge file used for filing narrow slot& notches and groo#es.

* 5 rough file used for cutting soft metals and trimming the rough edges of casting of soft metal.

*5 second cut file used for harder metals.

* 4n single cut file teeths are cut at an angle of about :;< to the centre line of the file.



* 4n double cut file teeths are cut at an angle of :; and the up cut at an angle of =; to the centre line.

* 0aps files useful for filing wood& plastic hard rubber etc.

1.> Scra!es these are used for sha#ing or parting off thin slices or flaks of metal to make a fine& smooth

surface. ?enerally these are made from old files.

1.: Hacksaw + 'acksaw blades these are made from high carbon steel 6or7 high speed steel. (he metal is

remo#ed during the forward stroke and the return stroke is an idle stroke.* Soft metals and plastics are being cut by coarse tooth saw.

* (ool steel& medium+hard steel& copper alloys are cut by the medium tooth saw.

1.= "arking tools+

Surface plate is used for testing the flatness of work itself and also used for marking out work. $arger 3obs

marking out table is used. 4t is made of gray cast iron.

* Scriber are use to scribe lines on metal.

* %unch is used in bench work for marking out work& locating center etc. Made of high carbon steel.

* ,entre punch angle @;<. /se to make a centre at a drilling point.

* ot punch angle is :;<. 4t is used to make perm ant marking.

* %rick punch angle is -;<+ 2;<. /seful for marking on 3obs of thin metal sheets.

* +Blocks are made of cast iron used for holding round bars during marking and drilling.

*5ngle plate is made of grey cast iron. 4t is used to hold the work in a #ertical position for laying out.

* (ry sAuare is use to set another edge or surface exactly at right angle to the already true edge or surface.

#.0 orging Tools:-

1.1 $n%il + 4t pro#ides support when force is applied to the forged component. 4t is made of cast steel or

wrought iron. 0ound hole pro#ided on the face of an#il is known as pritchel hole and sAuare hole is known

as hardie hole.

).). Swage &lock + Made of cast steel or cast iron. /sed for sAuaring& sizing& heading& bending and forming

operations.

).- Tongs + /sed to hold the 3ob and are made from mild steel.

).2 Swages (hey are used for work which has to be reduced and finished to round& sAuare or hexagonal

form. (hese are made from high carbon steel.

).> Chisels + (hese are made from high carbon steel.

* ,utting angle most commonly used of a cold chisel is :;<.

* ,utting angle of a cold chisel #arious according to the type of material to be cut. 5luminum + -;<&

copper + 2><& Brass+>;<& wrought 4ron mild steel + >><&,ast steel + :;<& tool steel + =;<.

* 'ot chisel included angle is :;<.

).: 'llers (hey are used for flocking down a piece of work.

).= latters + (hese are made of tool steel. (hese are used for finishing flat surface.



-.; Car!entr( Tools+

-.1 "arking and "eas'ring Tools+

Be%el S)'are + 4t is similar to try sAuare but has a blade that may be swi#eled to any angle from ;< to

1C;<.

"itre S)'are + /sed to mark and measure the angles of 2><.

-.) Com&ination S)'are + 4t is a combination of six parts& namely

6a7 a sAuare 6b7 a 2>< Be#el 6c7 a set sAuare 6d7 a rule 6e7 Straight edge 6f7 a centre finder

-.- *a'ges + 4t is used to mark lines parallel to the edge of a piece of wood.

* Marking gauge has one marking point.

*Mortise gauge has two marking points one fixed and other mo#able.

* ,utting gauge has a cutting knife held& in position by a wedge and used for gauging fine deep fines.

-.2 C'tting Tools+

Saws + 4t is specified by the length of the blade.

* 0ip saws are used to cut alone the grains of wood.

* ,ross cut saws are used+to cut across the grains of wood. 4t is also known as hand saw.

* %anet saw is used mainly for fine and accurate cuts& and sometimes for ripping as well as cross cutting.

*(enon saw is also known as Back saw. 4t is mostly used for cross cutting for finer and more accurate

finish. (eeth are in the form of eAuilateral triangle.

* o#etail saw is similar to tenon saw. /sed where greatest accuracy is reAuired.

* ,omposs saw is also known as turning saw it is used for cutting small cur#es.

* Bow saw is used for cutting Auick cur#es.

* ,oping saw is used for small radius cur#es.

* %ad saw is used for cutting keyholes.

-.> Chisels + (hey are dri#en into wood using blows.

* irmer chisel used for taking winder cuts and finishing flat surfaces.

* o#etail chisel used do#etail 3oints and other +groo#es.

* Mortize chisel used for to take hea#y cuts.

-. : +lanning Tools + (he planning tools or planes are cutting tools which are used for sha#ing or

smoothing plane surfaces.

-.= Striking Tools

* ,law hammers are used for dri#ing nails and extracting nails out of wood.

* Mallet is a wooden hammer.

-.C Holding Tools+

* Slash cramp is also known as Bar ,ramp or (+,ramp. 4t is used for holding wider works.



*?+,ramp is used of smaller work.

* 5 %incer is a tool used for pulling out nails from wood.

#. ",$S,",/T $/ /S+,CTO/

1.; Linear "eas'rement+

1.1 /on +recision nstr'ments + 5ccuracy is limited to 1rnm to ;.>mm.

* Steel rule is a direct measuring 4nstrument to read on accuracy of ;.>mm and 1D :2th of an inch. (hey

are made of hardened Steel.

* ,alipers are used to transfer and compare a dimension from one ob3ect to another.

* Jenny or hermaphrodite caliper is used for scribing line parallel to edge of a cylindrical 3ob.

* (elescopic gauge is used for measuring the inside size of the slots or holes.

* epth gauge is used to measure depth of holes& groo#es and slots.

1.) +recision instr'ments+

!xternal micrometer used to measure external dimensions like diameter of shafts& thinness of parts to an

accuracy of ;.;1mm.

6b7British standard i.e.& !nglish micrometer has an accuracy of ;.;;1inch.

5 Screw micrometer is used for measuring pitch diameter of screw threads.

5 depth micrometer is used to measure depth of holes to an accuracy of ;.;1mm and ;.;;1 inch.

4nside micrometer is used to measure diameter of holes up to an accuracy of ;.;1 mm.

ernier caliper is used to measure both outside and inside diameters of Shafts& thickness of parts etc. to

accuracy is up to ;.;) mm and ;.;;1inch.

Slip gauges are precision gauge blocks used for precise measurement of parts.

ial indicator is a mechanical comparator and accuracy is up to ;.;1 min

5 pneumatic comparator is specially used in automatic size control

).; $ng'lar "eas'rements+

).1 /on !recision nstr'ments+

6a7 Be#el protectors are used to measure angles but not #ery accurate.

5d3ustable be#el gauge is used for checking& comparing or transferring angles.

,ombination set consist of three parts& they are sAuare head& center head and be#el protector.

).) +recision nstr'ments+

ernier Be#el %rotector is used to measure of angle to an accuracy of 1D1) 6or7 > minuses of a degree.

Sine bar is a most accurate instrument used for measuring angles. 4t is specified by its distance between

centres of two rollers. 1;;mm length is most common.



6c7Sprit le#el is widely used for the static le#eling of machinery and other eAuipment.

5uto collimator is an optical instrument used for measurement of small angular differences& straightness and

alignment.

-.; Ta!er "eas'rement+

5 taper angle is measured by the following measuring instruments.

6a7 Be#el protector. 6b7 (ool room microscope

6c75uto collimating (elescope 6d7 Sine bar and dial gauge 6e7 0ollers slip gauges and micrometers.

2.; S'rface "eas'rement

6a7Straight edges are commonly used for testing the straightness and flatness of plate surfaces. latness is

checked by a light test.

6h7Surface gauge is used to scribe lines at a gi#en #ertical height.

>.; *a'ges ?auges are tools which are used for checking the size& shape and relati#e positions of #arious

parts. But not pro#ided with graduated ad3ustable members.

* %lug gauge is used for checking holes of different shape and size.

* 0ing gauge is used for testing external diameter.

* (aper gauge are used to test tapers of both internal and external. (hey are made in both plug and ring style.

* snap gauge are used for checking external dimensions. Shafts are mainly checked by snap gauge.

* (hread gauges are used to check the pitch diameter of threads.

* Screw pitch gauge is consists of a number of flat blades which are cut out to a gi#en pitch and pi#oted in aholder. 4t is used to check the pitch of screw threads.

* 0adius and fillet gauges are used to check the radii of cur#ature of con#ex and conca#e surfaces.

* eeler gauges are used to check clearance between matching surfaces.

* (he thickness of sheet metal is checked by means of plate gauge and wire diameter by means of wire

gauge.

2. ",T$LSMetal is a mineral which is used in all works of !ngineering. Metals are mainly two types i.e.& ferrous metals

and Eon errous metals.

1.; +h(sical !ro!erties + Feigh& construction& color& Magnetization& conducti#ity and melting point are

physical properties of metal.

).; "echanical !ro!erties

* 'ctilit(: + (he ability of metals to deform under tensile load is called ductility. (he metals with this

property can be easily drawn into wires. !x+Mild steel.

*Brittleness is the ability of a metal which break or fail before much deformation take place. !x + ,ast

4ron.

* ,lasticit( + (he ability of a material to regain its original shape after deformation when the external

forces are remo#ed. Steel is most elastic material.



* Stiffness 4t is the ability of material to resists deformation under stress.

* +lasticit( + 4t is the property of material which regains the deformation produced under load permanently.

(his property is necessary for forging metals.

* "allea&ilit( 4t is the ability of material to deform under compressi#e load. (he metals with this property

can make into thin sheets. !xample + 5luminum& tin lead.

* To'ghness it is property of material to resist fracture due to high impact loads like hammer blow.* esilience 4t is the property of a material to absorb energy and to resist shock and impact loads. (his

property is essential for spring metals.

* Cree! + Fhen a part is sub3ected to a constant stress at high temperature for a long period of time. 4t will

undergo a slow and permanent deformation called creep. (his property is considered in designing 4.,.

!ngines& turbines etc.

* Hardness + 4t is the ability of material to resist scratching& wear& abrasion& cutting& indentation and

penetration.

* atig'e + ailure of material under re#ersal stress is called fatigue.

* 3eld a&ilit( 4t is the ability of material to be 3oined by welding.

* Cast a&ilit( + ,ast ability of metal refers to the ease with which it can be cast into different shapes.

-. +ig ron + (he product of blast furnace is pig iron. 4ron ore& ,oke& $imestone Blast of air are reAuired

to produce pig 4ron. $ime stone acts as a flux and forms impurities into a liAuid slag. (he important ores of

4ron are 'ematite& Magnetite& $imonite& %yrite and Siderite.

2.1 Cast iron + (he product of the coupla is cast 4ron. %ig iron& steel scrap& ,oke and lime stone are

reAuired to produce cast 4ron. ,ast 4ron is an alloy of 4ron& carbon and silicon. (he carbon content ranges

from ) to 2G.

* T(!es of cast ron

6a7 ?ray cast 4ron 6b7 white cast 4ron 6c7 Spheroidal gray ,.4. 6d7 Malleable cast 4ron 6e7 5lloy cast 4ron.

2.# 3ro'ght ron + 4t is pure 4ron. 4t is approximately @@G. %ure 4ron and remaining carbon slag is left.

*4t is soft and can be easily forged and welded.

* 4t is manufactured by melting white pig 4ron in puddling furnace.

* used for+nuts& chains& crane hoots& railway +cowling& pipe and pipe fittings& boiler tubes+etc.

-.- Steel: Steel is fundamentally an alloy of 4ron ,arbon with the carbon content #arying up to 1.>G.

* Steel is manufactured by the following processes.

6a7 8pen 'earth process 6b7 Bessemer process 6c7 uplex process 6d7 !lectric process

6e7 $ process 6f7 ,rucible steel process

* Steel can be di#ided into two types i.e.& 6a7 %lain carbon steel 6b7 5lloy steel

* %lain carbon steels are classified based on carbon content is

1. $ow carbon steel

). Medium carbon steel

-. 'igh carbon steel.



Low Car&on steel + 4f carbon percentage is less than ;.15G is called dead mild steel. ,arbon percentage is

;.1>+ ;.->G then steels are called mild steel.

'igh ductile and soft.

/sed for Euts& bolts& ri#ets& ,hains& nails& wires& and thin Sheets.

"edi'm Car&on Steel + (he carbon percentage is from ;.->G to ;.:G.

0elati#ely harder& toughest and less ductile.

/sed for making connecting rods& shafts& axles& crank shafts& pulleys& wire tops rails etc.

High car&on steel + (he carbon percentage is from ;.:G to ;.@G for tool steels carbon percentage #aries

from ;.@G to 1.>G.

(his is #ery hard and tough.

4t acAuires permanent magnetic properties.

/sed for making springs& an#il faces files& cold chisels& punches& dies and cutting tools.

$lle( Steel + Steel that contains one or more alloying elements is called alloying steels.

'igh speed steel 6'SS7 is a alloy steel used for cutting tool. (he most common type is known as 1C + 2 +1

'SS and contains 1CG tungsten& 2G chromium& and ly anadium. 'SS is extensi#ely used for drills& $athe&

planner tools and milling cutters.

Stainless steel is a corrosion resistance steel it has 1CG ,hromium CG Eickel and most commonly known as

1CDC stainless steel. /sed for surgical 4nstruments& 9itchen eAuipment& utensils etc.

4n#ar contains nickel up to -:G. 4t has low coefficient of expansion. 4t is used for measuring 4nstruments&

clocks etc.

2.; /on-ferro's "etals (he metals that do+not contain 4ron are called Eon ferrous metals.

2.1 $l'min'm + 4t is mainly produced from bauxite ore. 4t is of white blue color. 4t occurs in abundance on

the surface of earth.

* 4t is good conductor of heat and electricity.

* $ight in weight& #ery malleable and can be rolled into thin sheet.

* Melting point is ::;<,.

* /sed for making parts of aero plane& electric wires& utensils etc.

2.) Co!!er + 4t is reddish in color& !xtracted from copper pyrites.

* ?ood conductor of heat& soft& flexible& ductile& tough and strong.

* Melting point is 1;C-< ,.

* /sed for electrical purposes& tubes and utensils.

2.- 4inc it is bluish white metal. 4t is mainly produced from zinc sulphide and zinc carbonate.

* 4t is good conductor of heat and electricity.

* 4t is used as a producti#e coating for 4ron and Steel sheets.

* 4t is used to make brass and bronze.

* 4ts melting point isH 2);< ,.



2.2 Tin + 4t is sil#ery white metal obtained from tin stone.

* Soft and malleable.

* 4ts melting point is )-;<,.

* /sed as a protecti#e coating for 4ron and steel and making bronze& gunmetal& bearing metal and solder.

2.> Lead + $ead is a hea#y metal and extracted from ?alena. 4t is of bluish brown colour.

* 4t is #ery soft& malleable& ductile and tough.

* Melting point is -);<,.

* /sed in manufacture of storage batteries& electric cable co#erings& soft solder& lead pipes& fuse wires etc.

*4t is a bright white metal. 4ts melting point is @:;<,.

>.; /on - erro's allo(+

S.

E

o

5lloy ,omposition /ses

1

)

-

2

>

:

=

C

@

1

;

111

)

1

-

uralumin

Brass

Muntz

Metal

Ea#al

Brass

Monel

Metal

Bronze

Bell metal.

?un metal

Solder

Babbit

metal

Eichrome

Fhite

metal

?erman

sil#er

[email protected]& ,u+2G& Mn+

;.>G

Mg + ;.>G& Si + ;-G.

,u+=;G& In +-;G

,u+:;G& In +2;G

,u+:;G& In+-@G& Sn+ 4

G

Ei+:;G& ,u+-CG& 51+

)G

,u+=; to @>G Sn +)> to

>G

,u+C;G& Sn+);G

,u +C-G& Sn+1;G& In+

)G

Sn+:- to 2)G& %b+-=to

>CG

Sn+CCG& ,u+2G& Sb+=G

Ei+C;G& ,r+);G

Sn+->G& ,u+>G& 54+

1;G

,u+>>G& In+)>G& Ei=+

);G

Building aero plane structures&

automobile parts etc

/tensils& ,ondenser tubes etc

!lectrical fittings& ,ondenser

tubes.

Marine pans

Steam turbine Blades and impeller

of pumps tc.

Making coins& statues and

ornaments etc.

Making bells and gongs.

Making guns& bearing and boiler

fittings.

Soldering.

Making crank shaft+ bearing

!lectrical hearten& 4ron& cookers

etc

$arge bearings of light load

8rnaments& and resistance coils

etc.

5luminum. ,u ,opper& Mn Manganese& Mg Magnesium& Si Silicon& Sn (in& %b lead& +,r+

,hromium.



5. ",T$L 6O//* +OC,SS,S

1. "etal 7oining !rocess Metal 3oining process is the process 3oining of similar or+dissimilar metal by the

application of heat. 4t is classified as follows

6a7 Felding 6b7 Soldering. 6c7 Brazing

#. 3elding 4t is process of 3oining similar metals by the application of heat& with or without the application

of pressure and with or without the addition of filler metal.

-. T(!es of welding fusion or non+pressure welding. (he metal at the Joint is heated to a molten state and

then allowed to solidify. Since no pressure is applied in this process

!x ?as welding& !lectric arc welding& (ermite welding

+ress're or !lastic welding (he metal pans are heated to a plastic state. (hen they are pressed together tomake the 3oint. 4t is also known as pressure welding. Eo filler metal is reAuired for pressure welding.

!x !lectric 0esistance welding& forge welding.

5. *as welding 4t is a type of fusion& non pressure welding. (his reAuired heat to melt the metal parts is

supplied by a high temperature flame obtained by a mixture of two gases.

* lame temperature of different gases

* 8xy + acetylene 6-);;<,7& 8xy hydrogen 61@;;<,7

* 8xy+Methane 6);;;<,7& 8xy+ water gas 6)-;;<,7

* 8xy+ acetylene is widely used for welding purposes.

* 8xy+ acetylene welding is particularly suitable for Joining metal Steels and plates of thickness ) to >;

mm.

* 8xy + hydrogen process is suitable up to plate thickness = mm only.

* 5cetylene is manufactured with the action of water on calcium carbide.

* 5cetylene is stored in cylinders in liAuid form.

* %ressures of oxygen and acetylene are respecti#ely 1>;;; knDm) and1:;;knDm).

* 8xygen cylinder is generally painted black& while acetylene cylinder is painted maroon.

5.1 T(!e of flame 8xygen and acetylene can be e3ected from the torch tip in three possible mixtures.

/at'ral flame (his flame has eAual Auantity of oxygen and acetylene. (his flame has two zones. (his is

used for welding steel& stainless steel& cast 4ron. Eon ferrous metal like cooper 5luminum. (his flame is

used in cutting operation also.

O8idi9ing flame 4n this flame oxygen and acetylene are in the ratio of 1.) to 1.>1 i.e. excess oxygen. (his

flame has two zones. 4t is used for welding copper brass and bronze.



Car&'ri9ing or ed'cing flame (he ratio of oxygen to acetylene is ;.@1 i.e. excess acetylene. (his flame

has three zones. 4t is mainly used for welding allot steel.

2.) *as welding Techni)'es

Leftward or forward welding 4t also called back hand welding. Blow pipe is held in right hand and the

welding rod is on left hand. (he weld is working from right to left. * 4nclination of the blow pipe with the work surface is between :; to =;.

* 4nclination of filler rod with the work surface is -;< to 2;.

ight ward or &ackward welding 4t is also known as forehand welding. (he weld is made from left to

right.

* 4nclination of the blow pipe with the work surface is between 2; to >;and filler rod with the work surface

is -; to 2;.

Vertical welding 4t does& not reAuire any edge preparation for plate thickness up to 1>mm.

*4nclination of the nozzle of the blow pipe with #ertical work surface is depends on plate thickness and is

in between )>to @;.

* iller rod with the #ertical work surface is nearly -;.

>.; ,lectric arc welding (he source of heat for electric arc welding is an electric arc. (he arc is produced

between an electrode and the work

* 5ir gap between work and the electrode is approximately -mm.

* (he temperature at the centre of the arc is>>;;c to :;;;,.

* 5, or , Supply can be used for arc welding

* or 5, welding supply& transformers are used to step down the usual supply #oltage 6);;+2;;#7 to the

normal open circuit winding #oltage >;+@8.

* Felding is going onK arc #oltage is of the order of 4C+2;#.

>.1 Com!arison of C and $C arc welding

* , arc welding is suitable for both ferrous and non ferrous metals. 5., arc welding is not suitable for non

ferrous metal.

* 5rc stability is more in .,. whereas less in 5.,

* Eon coated bare electrodes can be used in ,. 8nly coated electrodes are used in 5., arc welding.

* 4n , arc welding positi#e terminal connected to the work and negati#e terminal to the electrode.

Fhereas in 5., any terminal can be connected to the work or !lectrode.

* ., is less efficiency. Fhereas 5, more efficiency.

>) ,lectrodes for $rc welding !lectrodes for arc welding are classified into two categories

Cons'ma&le electrodes (hey get consumed during the welding operation. (hey are may be either bare or coated type.

* Bare electrode has limited applications like minor repair of poor Auality work of welding.

* !lectrode coated with flux material such as asbestos.



* lux coated electrodes main functions are to stabilize arc& pro#ide a protecting atmosphere and formatting

of slag.

/on-Cons'ma&le electrodes (hese are made of carbon& graphite or tungsten. Fhich do not consume

during welding process.

:.; $rc welding "ethods (he electric arc welding is classified in to

657 Metal 5rc welding 6B7 ,arbon 5rc welding 6,7Submerged 5rcwelding 67 Metal inert gas 6M4?7 5rc welding 6!7 (ungsten inert gas 6(4?7 5rc welding

metal arc welding.

:.1 "etal arc welding (he consumable flux coated electrode is used. Both 5, and , welding machines

are used. (he angle between gee+electrode and work should be =;<.

:.) Car&on arc welding 5 non consumable carbon electrode is used. !lectrode is connected to the negati#e

terminal and the work is the positi#e terminal. 8nly , supply is used in carbon arc welding. (he

(emperature produced is about -);;c.

:.- S'&merged arc welding 4t is sometimes called hidden arc welding. (he arc is formed between the end

of a continuous i.e. depositing surface& under layer of protecti#e mineral powder known as the flux or melt.(he bare electrode is fed from a reel down through the gun or nozzle.

:.2 "etal inert gas"*; welding 4t is a gas Shielded metal arc welding process which uses the high heat

of an electric arc between a continuously fed& consumable electrode wire and the material to be welded for

5luminum or copper& or argon helium mixture are used. (itanium reAuires pure argon.

:.> *as T'ngsten $rc welding T*; 4t is similar to M4? welding except+electric are between a non

consumable tungsten electrode and the material to be welded. 5rgon is more widely used for shielding. (his

process is not used as often on plate o#er :.2mm thick.

=.; esistance welding 4n resistance welding the metal parts to be 3oined are heated to a plastic state o#er a

limited area by their resistance to the flow of an electric current and mechanical pressure is used to complete

the weld. (here are two copper electrodes in the circuit

'eat generated in watt hours ' 4) 0(

Fhere 0 0esistance& 4 current in amps& ( time

oltage used is #ery low 2 to 1)#.

=.1 T(!e of resistance welding.

S!ot welding Spot welding is used to 3oin o#erlapping& sheets or plates of metal at small areas this weld be

used to weld steel and other metal strips up to 1) mm thick.

Seam welding 4t is a continuous type of spot welding o#er two o#erlapping metal sheets or plates. 4nstead

of using pointed !lectrode& roller type copper electrodes are used.

+ro7ection welding 4n this welding a number of spots can be welded in one closure of the press.

B'tt welding there are two types of butt welding namely& 6i7 upset Butt welding and 6ii7 flash butt welding.

!set B'tt welding (he two parts to be welded are placed in contact by clamping edge to edge in copper

Jaws. 4t is extensi#ely used for 3oining bars or pipes end to end.



lash B'tt wielding in this type& the two parts to be welded are clamped in copper Jaws of the welding

machine and brought together in a light. ,ontact or with a small air space between them. 4t is used for

welding body& tubes& wheels axles and flame in the automobile contraction work.

C.; Thermit welding 4t is a fusion welding process. (he welding is done by pouring super heated liAuid

thermit steel around the parts to be welded. (hermit steel is a mixture of finely di#ided aluminum powder

and 4ron oxide at the ratio of 1- by weight. 4t is used for welding #ery hea#y parts as Joining of rails& cables&

shafts& broken machinery frames and broken teeth of large gears etc.

@.; 3elding defects

+oor f'sion 4t is usually caused by insufficient heat and too fast tra#el of electrode.

nder c't 4t is due to excessi#e wea#ing speed& big electrode& and excessi#e current.

+orosit( (he formation of blow holes& gas pockets& on the surface of the weld. (his is due to the presence

of gases in the metal& moisture in the flux and presence of rust& grease.

Cracks ue to incorrect welding techniAue or using a filler metal ha#ing a different rate of contraction

compared to that of parent metal.

S!atter 4t refers to the small particles or globules of metal scattered around the #icinity of weld along its

length.

1;.; flame C'ing 4ron and steel sheets and plates can be cut by using oxy+acetylene is based on the fact

that ferrous metals are sub3ected to oxidation.

11.0 Soldering Soldering is the process of Joining two pieces of metal by adding a fusible alloy or metal

called solder. 4t is used as a filler rod. (he work pieces are not+ melted in the soldering process.

* 5 Soldering is an alloy of lead and tin.

* 4t has a low melting temperature in the+range of 1>; + ->;<,.

* Iinc chloride is used as a flux in Soldering

* Soldering 4ron bit is made up of copper because its ability to absorb and gi#e up heat.

11.1 T(!e of Soldering (he different compositions of solder for different purpose are

647 Soft solder lead -=G& tin :-G

6ii7 Medium solder lead >;G tin sock

6iii7%lumber"s solder lead =;kL tin -;G

6i#7 !lectrician"s Solder lead >CG.& tin 2)G +

1).; &ra9ing 4t the process of 3oining two similar or dissimilar metals by a fusible alloy called spelter. 4t

is similar to soldering except that speller is used instead of solder.

* (he Most commonly used flux in brazing is borax.

* luorides& chlorides and boric acid also used as a flux.

* (he melting point of the+ filler metal in brazing should be abo#e 2);<c.

* Sil#er alloys made of sil#er and copper with a milting range of:;;+C;;c are used for brazing any metals.



<. SH,,T ",T$L 3O=

1.; Sheet metal works is generally regarded as the working of metal& from 1: gauges to -; gauges& with

hand tools and simple machines into #arious forms by cutting& forming into shape& and Joining.

* Metals used in sheet metal work are black 4ron& gal#anized 4ron& S.S& ,opper& brass& 5luminum& tin plate

and lead.

* Iinc coated 4ron is known as gal#anized 4ron. (his is popularly known as ? 4 Sheet.

).; Sheet metal hand tools Basic tools used in sheet metal work.

6i7 Measuring tools Steel rule& folding rule& circumference rule& ernier caliper& micrometer& thickness

gauge& and sheet metal gauge. 6ii7Straight edge 6iii7 steel sAuare 647 scriber 6i#7 i#ider& 6#i7(rammel

points& 6#ii7 %unches 6#iii7 ,hisels& 6ix7 'ammers& 6x7 snips or shears 6xi7 pliers 6xii7 groo#es and ri#et sets

6xiii7 soldering 4ron

2.0 Sheet metal o!erations

-.1shearing 4t designates a cut in a straight line across& a strip& sheet or bar. (his procedure lea#es a clean

edge on the piece of metal that is sheared or cut. (he basic shearing operations are

C'ring off (his means se#ering a piece from a strip with a cut along a single line.

+arting 4t signifies that scrap is remo#ed between the two pieces to part them.

Blanking cutting a whole piece from sheet metal.

+'nching 4t is a operation of producing circular holes on a sheet metal by a punch and die.

/otching (his is a process of remo#ing metal to the desired shape from the side or edge of a sheet or strip.

Slitting Shearing is conducted between& rotary blades. 4t cuts the sheet metal length wise.

Lancing (his makes a cut part way across a strip.

ni&&ing ,utting any shape from sheet metal by nibbing machine.

Trimming 4t is the operation of curing away excess metal in a flange or flash from a piece.

-.) Bending 4t occurs when forces are applied to localized areas& such as in bending a piece of metal into a

right angle and forming occurs when complete items or parts are shaped.

-.- rawing it is a operation of producing thin walled hollow or #essel shaped parts from sheet metal.

-.2 S)'ee9ing 4t is a Auick and widely used way of forming ductile metal. (he sAueezing operations of

sizing& coining& bobbing& ri#eting etc.

2.; Sheet metal 6oints



Hem 4t is an edge or border made by following. (hree common type of hems are single hem& double hem

and wired edge.

Seam 4t is a 3oint made by fasting two edges together. Most common type of seam are

La! Seam $ap 3oint by soldering.

Single seam /sed to 3oin a bottom to #ertical bodies

The do'&le Seam its formed edge is bent upward against the body.

The do%etail seam /sed to 3oin flat plate to a cylindrical piece.

>. ",CH$/C$L 3O=/* O ",T$LS

1.; 4t is simply plastic deformation performed to change dimensions& properties and surface condition of ametal by means of mechanical pressure.

* 4f plastic deformation abo#e re+crystallization temperature but below melting point is hot working.

* 4f plastic deformation below re+crystallization temperature is cold working.

Hot working methods

Hot rolling 0olling is the most rapid method of forming metal into desired shape by plastic deformation in

between rolls.

* bars& plates& sheets& rails and other structural sections like 4+section& channel section& !Aual angle and (+

sections. !tc is manufactured by rolling.

+iercing 4t is the process employed for the manufacturing of seamless tubes.

rawing 4t is the process of making cup shaped parts from flat sheet metal blanks.

Hot s!inning it is a process of making circular sections from sheet metal. 4t is carried on lathe

,8tr'sion 4t is a process in which heated billet or slug of metal is forced by high pressure through anorifice that is shaped to pro#ide the desired form

∗ 0ods& tubes& brass cartridges& lead co#er cables& aircraft parts and many hardware items are typical

product of extrusion.

∗ Seamless tubes in mass production are manufactured by the extrusion process.

1.) Cold working methods

Cold drawing (he operation in#ol#es the forcing of metal through a die by means of a tensile force applied

to the exit side of the die. 5ll the wire that is a#ailable is produced by cold drawing through dies.

Cold S!inning 4t is the operation of shaping #ery thin metal by pressing it against a form while it is

rotating.



* /sed in making of bells on musical instruments& light fixtures& kitchen ware& and large processing kettles.

Cold e8tr'sion 4t is similar to that of hot extrusion. ,ollapsible medical tubes and toothpaste tubes are

made in this method.

Cold heading 4t is a cold forging process& used primarily for the manufacture of bolts& screws& ri#ets and

similar items.

Thread rolling 4t is used for mass production of threaded parts.otar( swaging 4t is the process used to reduce the cross sectional area of rods and tubes.

Coining %rocess in#ol#es the impression and rising of images or characters from a punch and die into the

metal.

* ,oins& medals and other such similar parts are produced by this process.

=. H,$T T,$T",/T

1.; heat Treatment 'eat treatment can be defined as the process of changing the structure and properties of

metal by controlled heating and cooling.

+'r!oses of heat treatment

* (o relie#e the internal stresses.

* (o refine the grain size so as to impro#e the mechanical properties

* (o impro#e the mach inability.

* (o increase corrosion and wear resistance.

1.1Critical tem!erat're Fhen steel is heated at high temperature& then at a certain temperature change

starts in the internal structure. (he temperature at which this change starts take place is called critical

temperature.

1.) Lower critical tem!erat're (he temperature at which the change in structure start taking place is

called lower critical temperature. (his is about =)- <,.

1.- Higher critical tem!erat're (he temperature at which constituents 4ron and carbon mix up completelyand becomes one. (his point of temperature is called upper critical point.

1.2 Heat Treatment !rocesses

$nnealing 4t is the process of heating steel slightly abo#e its critical range holding it there until the

temperature of the piece is uniform throughout and then cooling at a slow rate.

* (he primary purpose of annealing is to soften and to increase the ductility.

* 4t also relie#es internal stress.

/ormali9ing 4t is the process of heating the metal abo#e the upper critical temperature and cooling in air.

* (he purpose is to refine the grain structure& relie#e the internal tresses and to impro#e the machine ability.



Hardening 4t is the process of heating steel to a temperature within or abo#e its critical range and then

cooling it rapidly in oil or water or other suitable solutions.

* (he purpose of 'arding is to de#elop high hardness& wear resistance and ability to cut other materials.

Tem!ering 4t is the process of heating the hardened steel below lower critical temperature& holding at this

temperature for sufficient time and slow coolie

* (empering reduces the hardness& brittleness and increases toughness.Car&'ri9ing 4t is a process whereby carbon is absorbed into the surface of steel alloys. 4t consists in

heating of steel to a red heat& in contact with some carboneous material.

* (he process is carried out on low carbon steels for producing hard surface.

/itriding 4t is a process of case hardening ferrous alloy of suitable composition by absorption of nitrogen.

(his is done by heating in an atmosphere of ammonia.

C(aniding 4t is a ,ase hardening process in which both carbon and Eitrogen added to the surface layers of

the steel.

nd'ction hardening 4t is a surface herding process in which the part to be surface hardened is placed

within an induction coil through which a high freAuency current is passed.

lame hardening 4t is a surface 'arding process in which the part is heated to hardening temperature with

an oxy+acetylene flame.

?. o'ndr(

1.; o'ndr( 4t deals with the process of making castings in moulds prepared by patterns.

1.1 Casting 4t is the process of pouring molten metal& into mould and allowing it to solidify

* 4n order to prepare a component by casting the following are reAuired.

6a7 %attern 6b7 molding sand 6c7 molten+material

1.# T(!es of !atterns

Most commonly used types of patterns are single piece pattern& split pattern

Match plate pattern& cope and drag pattern& gated pattern& loose piece pattern& sweep pattern& shall pattern

etc.

* Fooden pattern are used for small sized production schedules

* Metal patters are used for large size production

* Match plate patterns are used for small castings in large Auantities.

* Sweep patterns are used for symmetrical mouth particularly in large sizes.

1.- +attern allowance

Shrinkage allowance 4t is pro#ided to compensate for the #olumetric loss of metal during cooling in the

moulds. 4t is added to pattern made larger size by an amount eAual to that of shrinkage.



"achining allowance 4t is pro#ided on the pattern in order to get reAuired surface finish for the casting. 4t

is added to pattern.

raft allowance 5ll #ertical Surfaces of the pattern are pro#ided taper allowance so that pattern can be

remo#ing easily. 4t is a positi#e allowance.

Color codes of !atterns

* Surface to be left unfinished + Black * Surface to be machine + red

* Seats for loose pieces+ 0ed stripes on yellow back ground.

* ,ore prints+ + Nellow

1.2 "o'lding tools and e)'i!ments

Sho%el used for mixing and tempering moulding sand.

iddle 5 riddle sometimes called a screen. /sed for remo#ing foreign material such as this& shot metal&

splinters of wood etc.& from moulding sand.

ammers /sed to pack the sand e#enly around the pattern

Slick /sed for repairing and finishing the mould surface and edges after the pattern has been withdrawn.

Lifters /sed for remo#ing the sand particles from the mould.

Swa& /sed for moisturizing the edges of sand mould.

Vent rod /sed to make series of holes in the sand of a mould to permit gases to escape.

raw s!ike /sed to remo#e the pattern from the mould

Trowels /sed to shape and smoothen the surface of the mould and for doing minor repairs

Bellow /sed to blow loose particles of sand from the pattern and the mould ca#ity.

"o'lding Bo8 (op part of Box is called cope& bottom part is called drag and middle part is called cheek.

1.> T@+,S O "OL/* S$/

*reen Sand 4t is a mixture of silica sand with 1C to -;G ,lay& and moisture : toCG. used for small and

medium size castings.

r( sand (his is free from moisture& used for making large casting

Lome sand it contains >;Gclay. 4t is particularly employed for large casting.

acing sand forms the face of the mould. /sed to pre#ent the metal from burning into the sand.

Core Sand used for making cores sometimes called oil sand.

+arting sand /sed to keep the green sand from sticking to the pattern and also to allow the sand on the parting surface of the cope and drag to separate without clinging.

1.: +O+,T,S O "OL/* S$/



+orosit( 4t is the property of the sand which allows the gases and steam to escape through the sand.

low a&ilit( 4t is the ability to beha#e like a fluid so that& it will flow to all portions of a mould and take up

reAuired shape.

Colla!si&ilit( 4t is the property due to which the sand mould collapses after solidification of the casting to

allow a free ,ontraction of the metal.

$dhesi%eness %roperty due to which it is capable of adhering to another body.Cohesi%eness (his is the ability of sand particle to stick together.

efractoriness (he ability of sand to with stand high temperature of the molten metal without fusing.

1.= "OL/* +OC,SS

loor mo'lding %roduction of Medium and large castings.

+it mo'lding moulds of large 3obs are generally prepared in a pit dug in the foundry floor.

Bench mo'lding or small casting which are light in weight.

1.? "OL/* "$CH/,S

S)'ee9er "achine moulding sand in the flask is sAueezed until the moulds attain the desired density.

6olt machine (he action of raising and sudden dropping of the table the sand get packed and rammed. (he

sand is rammed hardest at the parting plane and around the pattern and remains less dense in the top.

6olt s)'ee9e machine + a combination of sAueeze and Jolt action is often employed.

Sand Slinger 0amming is obtained by the impact of sand which falls at a #ery high #elocity.

1.@ S+,C$L "OL/* +OC,SS,S

* ,8) moulding process uses sodium silicate as the binder. Silica gel formation occurs in ,8) moulding.

* (hermo setting 0esin is used as the binder for shell moulding.

* Fax patterns are used in 4n#estment casting.

).; +,"$/,/T "OL C$ST/*

* ery high rate of production is achie#ed in die casting and tolerances of the order of ;.;)> mm.

* Semi centrifugal casting is used to obtain gears& disked wheels& pulleys etc.

* (rue centrifugal is 4deal for hollow cylindrical castings such as bushings& gun barrels& cast 4ron pipes etc.

* 4n centrifugal casting& cores are not reAuired for hollow castings.

).1 *$T/* $/ S,/* O C$ST/*



* ?ating system is pro#ided to continuous& uniform feed of molten metal with as little turbulence as

possible to the mould ca#ity.

* Sprue is a #ertical passage through the cope and connects the pouring basin with the runner or gate.

* 0iser permits the molten metal to rise abo#e the highest point in the casting after the mould ca#ity is

filled up.

A. "$CH/, TOOLS

Lathe "achine

1.; $athe (he main function of a lathe is to remo#e metal in the form of chips from a work piece to gi#e it

the reAuired shape and size& this is accomplished by holding the work securely and rigidly on the lathe and

then rotating it against a cutting tool.

1.1 S!ecification of a lathe (he size of a lathe is specified by

6i7 'eight of centers from the bed 6ii7 Maximum swing o#er bed

6iii7 Maximum swing o#er carriage. 6i#7 Maximum distance between centers

6#7 8#erall length of the bed.

1.) T(!es of lathe

* Speed lathe has no carriage& gearboxK used for wood working& polishing and spinning.

* !ngine or center lathe widely used for many operations like turning& facing& taper turning & thread

cutting& drilling etc.

* Bench lathe is used for small and precision works.

* (ool room lathe is used for #ery precision turning of tools& gauges and dies.

* (urret and capstan lathe are production lathes used for mass production.

* 5utomatic lathes are high speed& hea#y duty and mass production lathes with complete automatic.

* Special purpose lathes are designed to perform certain specified operations only. !.g. crank shaft&

uplicating lathe.

1.- + 'nctions of lathe !arts

Bed Base of the lathe. 5ll parts are located on the bed. (he bed has flat or in#erted guide ways.

* 8uter ways pro#ides bearing and sliding surface for the carriage

* 4nner ways pro#ide ways for tail stock.

* 5utomatic chip disposal is ad#antage in in#erted +guide ways.

* Made gray cast iron alloy with nickel and chromium.

* (he bed material should ha#e high compressi#e strengths& wear resistance and good absorb of #ibration.



Head Stock Secured permanently at the left end of the bed.

* 4t carries a hollow spindle and a li#e centre can be fitted into the hollow spindle.

* (he spindle got external thread and taper is 1);.

* a back gear is pro#ide minimum speeds to the spindle.

* 'ead stock can run at different speeds using 6a7 Belt dri#e on cone pulley 6b7 5ll geared 'ead stock 6c7

ariable speed motor.

*Tail Stock $ocated on the inner ways at the right hand end of the bed.

* it is used for supporting the right end of the work piece by means of a dead centre.

* 4t holds a tool for performing operations liked drilling etc.

* 4t can be also used for taper turning operation.

Carriage it is supported on the lathe bed ways and can mo#e in a direction parallel to the lathe a8is. 4t

consists of saddle& cross slide& compound rest& tool post apron.

* Saddle carries the cross slide& compound rest and tool post. 4t mo#e along the guide ways.

* ,ross slide carries the compound rest and tool post. 4t can be mo#ed by hand or by power feed.

* ,ompound rest is mounted on the cross slide. 4t carries a circular base called swi#el plate which is

graduated in degrees. 4t is used to set the tool for angular cuts& 4t mo#ed by means of hand wheel.

* (ool post is fitted o#er the compound rest. (he tool is clamped in the tool post.

$ower part of the carriage is termed as the apron. 4t is attached to saddle and hangs in front of the bed.

eed mechanism (he lathe tool can be gi#en three types of feed& namely& longitudinal& cross and angular.

* eed rod is a plain long shaft used to mo#e the carriage or cross slide all operations expect thread cutting.

* (he lead screw is a long thread shaft is used to trans#erse the tool along the work to produce screw

threads. (he half nut or split nut makes the carriage to engage or disengage the lead screw.

1.2 T(!es of feeds when the tool mo#es parallel to the lathe bed axis& called longitudinal feed& this is

achie#ed by mo#ing the carriage.

* Fhen the tool mo#es perpendicular to the axis of the lathe bed axis the mo#ement is called cross feed&

this is achie#ed by mo#ing the cross slide.

* Fhen the tool mo#es at an angle to the axis of the lathe& the mo#ement is called angular feed& this is

achie#ed by mo#ing the compound slide.

1.> 3ork holding and s'!!orting de%ices + (he de#ices employed for holding and supporting the work

piece and the tool on the lathe are also called its accessories.

Ch'cks Forks of short length& large diameter and regular and irregular shapes can be held in chucks the

chuck is mounted on the spindle of the lathe.

* (hree 3aw is also called self centering chuck. 4t consists of a cylindrical body ha#ing three 3aws fixedradially at its front. Fhen the chuck key is tightened the work is centered automatically.

* our 3aw is also called independent chuck. 4rregular or eccentric 3obs can be held in this chuck.

* ,ollect chuck used for holding bars of small sizes. 4t is normally used in capstone and automatic lathe.



* Magnetic chuck is used for holding thin 3obs of magnetic materials.

* ,enters are used for work holding in a lathe. 5 li#e center rotates with the work piece and a dead centre is

stationary which supports the right end of the work piece.

* (he included angle of the centre is :o degree and is machined to standard morse taper.

* 8rdinary centre is used for general works and half centre is used for facing operation without the remo#al

of the centre.ace +late 4t is a circular plat screwed to the lathe spindle. 4t consists of radial& plain and ( slots. $arge and

irregular 3obs which can hold on face plate by bolts and clamps.

$ngle +late 4t has two faces at right angle to each other& holes and slots are pro#ided on both faces to held

the work in #ertical

"andrels 4t is used for holding hollow work piece between centers.

Catch +late or ri%ing +late 4t is a circular plate and transfer motion to the dog fitted with the work piece.

4t is used to dri#e the work piece through the dog or carrier& when the work piece is held between centers.

Carrier or og 4t is used to transfer motion from the rotating catch plate.

S'!!orting de%ices /sed to long support work pieces.

* Steady rest is fastened to the lathe bed at a con#enient point.

* ollower rest is bolted to the carriage and thus it supports the work immediately behind the tool

throughout the trans#erse.

1.: Lathe O!erations

T'rning (ool is fed parallel to the lathe axis and cylindrical surface is produced.

acing 4t is the operation of machining of the end face of work to make it flat. (he tool is feed

perpendicular to the axis of lathe.

*roo%ing 4t is the process of reduces the diameter of a work piece o#er a #ery narrow surface. 4t is also

called under cutting or necking.

+arting 4t is the operation of cutting the work piece. 5fter it is machined to the desired size and shape.

=n'rling 4t is the process of embossing a diamond shaped regular pattern on the surface of a work piece. 4t

is done to gi#e a good gripping surface on the work piece.

rilling 4t is the operation of making a hole in the work piece. 4t is done when the 3ob rotates the drill bit is

fed into the work pieces by turning the tail stock hand wheel.

Boring 4t is the operations of enlarging a hole& produced by drilling& boring is used when correct drill is not

a#ailable.

eaming 4t is the operation of finishing a drilling or bored hole to accurate size. (he reamer is held in the

tail stock spindle.

* Magnetic chuck is used for holding thin 3obs of magnetic materials

Chamfering 4t is the operation of be#eling the extreme end of the work to protect the end of the work piece

from being damaged. 4t is an essential operation to be performed after thread cutting.

Ta!er T'rning 5 taper is defined as the uniform Se in the diameter of a work piece measured along its

length.



1.= $ngle of Ta!er 4f "" is large diameter& OdO is small diameter& Pl " is length of tapered part& then

(an Q D−d

l

Fhere PQO is angle of taper or half taper angle

Conicit( 4t the ratio of the difference between diameters of the taper to the length of taper.

,onicity 697 D−d

l

Ta!er t'rning methods

6a7Ta!er t'rning &( the com!o'nd rest (he compound rest may be swi#eled and set at the desired half

taper angle and tool is fed by rotating the compound rest wheel. 4t is suitable for short but steep tapers.

&; orm tool (his method is applicable for short work only taper turning is done by a form tool.

c;Ta!er attachment 4t is suitable for any length of the 3ob. 4nternal taper can also be turned.

d; Tail Stock Set O%er 4n this method the tail stock may be set o#er by loosing the nut from its centre line.

/sed for turning small taper on long 3obs and external taper only.

Set o#er 6s7 D−d

2

1.C Thread C'tting 4t is the operation to produce helical groo#e on a cylindrical or conical surface by

feeding the tool longitudinally& the rotation of lead screw is used to tra#erse the toot along the work to

produce screw threads.

*(he longitudinal feed should be eAual to the pitch bf the thread to be cut per e#olution of the work piece.

Speed of spindle %itch of lead screw

Speed of lead screw %itch of thread to be cut

* 4n case of cutting right hand threads& both the spindle and the lead screw will rotate in the same direction

and carriage must mo#e towards head stock.

* or cutting left hand threads& the spindle and lead screw will rotate opposite to each other and carrage

must mo#e away from the head stock.

1.@ Ca!stan and t'rret lathes in these lathes tail stock is absent and it is replaced by hexagonal turret.

* 5utomatic indexing and bar feeding mechanism is used to reduce the time reAuired to produce a

component.



* 5ltogether 12 different tools can be mounted in the lathes.

* /sed for mass production.

1.A T'rret lathe Vs Ca!stan Lathe

* (he turret of turret lathe is directly mounted on the bed. (he turret of a capstan1athe is mounted on a

short slide which slides on saddle.

* (urret lathe pro#ide almost rigidity to the tool support& in capstan lathe& o#er hanging of ram present anon

rigid ,onstruction.

(urret lathe is suitable for hea#y 3obs. ,apstan lathe is suitable for bar works.

1.1; efinitions

Steed Speed is the rate of rotation of work piece& express in re#olution per minute 6rpm7 and denoted by E.

C'tting S!eed 4t is the speed at which metal is remo#ed by the tool from the work piece. &

,utting speed 6#7 πDN

1000 mDmin

Fhere is the diameter of the work piece in mm.

eed eed is the distance the tool ad#ances for each re#olution of the work piece. 4t is express in mmDre#.

e!t of c't 4t is the perpendicular distance measured from the machined surface to the uncut surface of

work. 4t is expressed in mm.

epths of cut d1−

d2

2

4f d1 diameter of work before machining& d) diameter of work after machining.

LL/* "$CH/,

).; rilling 4t is the operation of producing hole in the work piece by using a rotating cutter called drill. 4n

the drilling machine& the work piece is held stationary and as the drill rotates it is fed into the work piece.

#.1 T(!e of drilling machines:

%ortable drilling machine it is #ery small and compact drilling machine. it may be operated by hand or by

an electric motor.

* (he maximum size of drill it ,all hold is up to 1Cmm.

* (his machine is specified by the maximum drilling capacity.

* Sensifire rilling "achine it is a light seed machine tool. it is mounted on a bench it is called bench

type and if mounted on face it is floor type.

* 4t is specified by the diameter of the largest work piece that can be drilled.

* 4t can drill holes from 1.>mm to 1>mm diameter.



* (he drill is fed into the work piece by hand only using rack and pinion arrangement.

!right drilling machine 4t is similar to sensiti#e drilling machine except that it has power feed

mechanism for rotating drill and it designed for medium size work.

* 0ound column drilling machine is also known as pillar drilling machine.

* (he box column machine is more rigid than a round column machine.

* (he maximum size of holes can be drill up to >;mm.

adial rilling "achine 4t is used for drilling large and hea#y work pieces.

* (hree mo#ements are possible in a radial drilling machine to locate the drill Auickly o#er any point on the

work.

* 4t has an additional swi#eling ad3ustment in either the head or the arm and can drill holes at any angle.

* 4t is specified by the length of the arm and column diameter.

*ang rilling taws "achine Fhen a number of single spindle drilling machine columns are placed side

by side on a common base and ha#e a common work table. 5 series of operation can be done on the 3ob.

"'lti s!indle tingling machine (hese machines ha#e se#eral spindles dri#en by a single motor and all+

spindles are fed simultaneously.

).) rilling "achine O!erations 8perations that can be performed in a drilling machine are 6a7 rilling

6b7 0eaming 6c7,ounter boring 6d7 ,ounter sinking 6d7 (apping

Co'nter Boring 4t is the operation of enlarging one end of a drilled hole. (he enlarged hole forms a sAuare

shoulder with the original hole. ,ounter boring is done to accommodate the heads of bolts& studs and pins.

Co'nter Sinking 4t is the operation of making a cone shape enlargement of the end of a hole. 4t is done to

accommodate flat head screw or counter sank ri#et fitted into the hole.

Ta!!ing: 4t is the operation of cutting internal threads by means of a cutting tool called tap.

Ta! grill si9e the size of the tap is eAual to the outside diameter of its threads. (herefore the drilled hole

must be smaller than the tap by twice the depth of the thread.

rill size (ap size + ) x depth of thread

).-Tool holding e%ices (he different methods are used for holding the drill in a drill spindle are

6a7 B( directl( fitting in the S!indle (he tool shank is forced into the tapered hole of the spindle and the

tool is gripped by friction. (he tool may be mo#e from the taper hole using a drift.

6b7 rill Slee%e 4f the taper shank of the tool is smaller than the taper in the spindle hole& a taper drill slee#e

is used.

6c7 rill Socket Fhen the tapered tool shank is larger than spindle taper& drill sockets are used to hold the

tool.

6d7 rill Ch'ck (he drill chuck is used to hold smaller size driers. 4t has two or more ad3ustable 3aws set

radially to hold straight shank drills.

).2 Twist rill /omenclat'res

6a7Tang 4t is the flattened end of taper shank. 4t fits into the slot in the machine spindle.



6b7 Shank 4t may be to tapered or straight. Morse taper is used for taper shank.

6c7Li! of c'tting edge 4t is the edge which actually cuts the material.

6d7 l'tes lutes are helical groo#es cut on the body of the drill. (he functions of flutes are to form the

cutting edges& to allow the chips to escape and to allow the cutting fluid to reach the cutting edges.

e; +oint $ngle %oint is the cutting end of the drill and point angle is the angle it between the cutting lips.

(he usual point angle is 11C degrees& but for harder& steel alloys& the angle increases.).> rill Si9es 4n metric system drills are commonly manufactured froth ;.) to 1;; mm. in British system

the drills are manufactured in three different sizes

6a7 /'m&er si9es (he drill size #aries from Eo. 1 to Eo. C;.

6b7 Letter si9es 4n this system the drill sizes range from 5 to I.

6c7 ractional si9es 4n this system the drill sizes range from 1D:2 inch to > inch.

6d7 C'tting S!eed 4t is expressed in mDmin

,utting speed 67πDN

1000 mDmin

is the diameter of the drill. E is the rpm of the drill spindle.

eed (he feed of a drill is the distance the drill mo#es into the work at each re#olution of the spindle. 4t is

expressed in mmDre# or per min.

(he feed per min feed per re# x rpm

epth of ,ut (he depth of cut in drilling is eAual to one half of the drill diameter.

(d

2 mm

-.; Boring machines (hey are used to bore holes in large and hea#y parts like engine drams& engine

cylinders& machine housing.

-.1 t(!es of Boring machines:

Hori9ontal Boring "achines Fork is supported on a table which is stationary and the tool re#ol#es in

horizontal axis.

Vertical Boring "achine (he work rotates on a horizontal table about a #ertical axis and the tool is

stationary except for feeds.

6ig &oring "achine it is the most actuate of all machine tools. /sed for production of Jigs& ixtures& (ools

and other precision parts. (he machining accuracy is a firm.

11. SH$+/* "$CH/,



2.; Sha!er Shaper is a reciprocating type of machine tool intended& primarily to produce flat surface. 'ere

tool is allowed to reciprocate.

2.1 Classification of Sha!ers Shapers are classified as follows.

647 according to the type of design of the table

6a7 Standard shaper. 6b7 /ni#ersal shaper

6ii7 5ccording to the position and tra#el of the ram

6a7 'orizontal type 6b7 ertical type

6iii7 5ccording to the type of dri#ing mechanism used for gi#ing reciprocating motion to the tarn.

6a7,rank type 6b7 'ydraulic type 6c7 ?eared type

6i#7 5ccording to the esign of table

657 Standard Sha!er (he table as two mo#ements only& #ertical and horizontal to gi#e the feed.

6b7 ni%ersal sha!er (able can be tilted about two more axes. 8ne axis is parallel to the ram axis and other

perpendicular to the first axis. 5 uni#ersal shaper is mostly used in tool room work.

$ccording to the !osition and tra%el or the ram

Hori9ontal t(!e ram reciprocates along 'orizontal direction. (hey are used mainly to produce flat surface.

Vertical T(!e ram reciprocates along #ertical axis. (hey are used for machining internal surface& keyways&

slots and groo#es.

$ccording to the t(!e of dri%ing mechanism 'sed for gi%ing reci!rocating motion to the ram.

Crank Sha!er 4t uses a crank mechanism to con#ert circular motion of a large gear called bull gear into

reciprocating motion.

*eared Sha!er 0eciprocating motion of the ram is obtained using rack and pinion mechanism.

H(dra'lic Sha!er 0eciprocating motion is obtained using hydraulic power. 4nfinite number of cutting

speeds can be obtained from zero to the maximum #alue and the control is easier.

2.-. S!ecifications of a sha!er (he size of the shaper is specified as follows.

6i7 Maximum length of stroke. 6ii7 (he maximum size of cube that can be held in a shaper.5 number of other details are reAuired to specify a shaper fully.

6i7Maximum #ertical ad3ustment of the table 6ii7 %ower of the dri#e motor

6iii7 (ype of dri#ing mechanism 6i#7 (ype of shaper

6#7 loor space and net weight

2.2 'ick et'rn "echanism (he Auick return of the ram can be obtained by any one of the following

mechanisms

6a7 ,rank slotted link mechanism 6b7 Fhitworth Auick return mechanism

6c7'ydraulic mechanism



(he a#erage time ratio of cutting stroke to return stroke in a shaper is -).

2.> Sha!er o!erations (he basic operations performed on a shaper are machining horizontal surface&

#ertical surface& angular surface& cutting slots keyways and machining irregular surface.

2.: C'tting S!eed ,utting speed is the speed at which the tool tra#erses through the material.

,utting Speed $ength of the cutting stroke

(ime taken for the cutting stoke

eed 4t is the relati#e mo#ement of tool or work in a direction perpendicular to the mo#ement of the ram. 4t

is express in mm per stroke. (he feed is always gi#en at end of return stroke.

e!th of C't: 4t is the thickness of metal remo#ed in one cut 4t is expressed in mm.

1#. SLOTT/* "$CH/,

>.; Slotter Slotting machine is a reciprocating type of machine tool similar to a shaper. (he main difference

is that in a slotter the ram holding the tool reciprocates in a #ertical axis& where as in a shaper the ram

holding the tool reciprocates in a horizontal axis.

>.1 T(!es of slotters

+'ncher Slotter (hey are hea#y duty machines& eAuipped with a powerful motor and can cut metal at a

#ery high speed.. 4t consists of a sAuare or circular table.

+recision Slotter 4t is a lighter machine and it is operated at high speeds. 4t is designed to take light cutsgi#ing accurate finish. these are usually fitted whit worth Auick return mechanism.

<.# Slotter S!ecifications (he size of a slotter is specified by the maximum length of the stroke of the ram.

(he size of a slotter usually ranges from C;to @;;mm.

(o specify the machine fully the following particulars are also gi#en.

617 (he diameter of the table in mm 6ii7 ,ross and longitudinal mo#ement of the table

6iii7 Eumber of speeds and feeds 647 %ower of the motor and

6#7 loor space reAuired .

<.2 Slotter O!erations (he following operations are performed on a slotter.

647 flat surface machining 6ii7 ,ircular surface machining

6iii7 4rregular surface and can machining 647 ,utting slots& keyways and groo#es

12. +L$//* "$CH/,

>.0 %laner is the largest reciprocating type machine tool. 4t is primarily intended to produce plane and flat

surface by a single point cutting pool. (he main difference between a shaper and a planer is that in a planer

the work is mo#ed against a stationary tool and is the fed into the work. Fhere as in a shaper the tool mo#es

across the stationary work and fed across the tool.



:.1 T(!es of !lanning machine

Standard or o'&le ho'sing !laner 4t consists of two massi#e #ertical housing connected by a cross rail.

O!en side !laner 4t has a housing on one side of the base only as a cantile#er. 4t allows large and wide

3obs.

+it +laner (he table is made stationary and the columns carrying the cross rail are made to reciprocate. 4t is

used for #ery large work.,dge or !late !laner 4t is used for sAuaring and be#eling the edges of steel plates for different pressure

#essels and ship building works.

i%ided ta&le !laner 4t consists of two tables on the bed which may be reciprocated separately or together.

(his type of design sa#es idle time while setting the work.

:.) ri%ing "echanism Mechanisms used for dri#ing the table of planer are

6a7 ,rank dri#e 6b7 8pen ,ross belt dri#e 6c7 ., re#ersible motor dri#e

6d7 'ydraulic dri#e.

:.- S!ecification of a !laner 4ts size is gi#en by the largest rectangular solid that can reciprocate under the

tool. 4t is known by

* (he horizontal distance between the two #ertical housings.

* ertical distance between the table top and the cross rail when the latter is in its top most position.

* Maximum length of table tra#el or length of stroke.

:.2 +laner O!erations (he common operations performed in a planer are

617 %lanning flat horizontal surface. 6ii7 %lanning #ertical surface

6iii7 %lanning cur#ed surface 6i#7 %lanning slots groo#es

6#7 %laning at an angle 6#i7 Machining do#etails

>.< +laner Vs Sha!er:

* %laner is specially adapted to large work. Fhereas the shaper can do only small work.

* 8n the planer the work is mo#ed against stationary tool but on shaper the tool mo#es across the work which is stationary.

* 4n a planer& work setting reAuired much of skill and where as shaper work may be clamped easily and

Auickly.

* 8n the planer the Auick return mechanism is incorporated for the table but in a shaper the Auick return

mechanism is used for dri#ing the ram.

* %laner tool are much more robust that used in a shaper.

12. "LL/* "$CH/,



D.0 "illing 5 milling is a machine tool that remo#es metal in the form of chips by a rotating multi point

cutter. 4t remo#ed metal in the form of chips by a rotating multipoint cutter. 4t remo#es metal at a #ery fast

rate.

=.1 T(!es of milling machines

,olumn and knee type 4t consists of a column and a knee which can be mo#ed up and down& a long cross

and longitudinal directions.

6a7 %lain milling machine table consists of three mo#ements only

6b7 /ni#ersal milling machine fourth motion of table i.e. 0otation is apart from standard table motions.

6c7 ertical milling machine (he spindle of the machine is #ertical. (he machine is used for machining

groo#es& slots and flat surface.

=.) S!ecification of milling machine (he size of column and knee type milling machine is specified by

6i7 Maximum length of longitudinal& cross and #ertical tra#els of the table.

=.- "illing O!erations (he different operations performed in the milling machine are

+lain milling %lain milling is the operation of producing plain& flat and horizontal surface parallel to the

axis of rotation of the cutter& including slots and groo#es. (his also called slab milling& when #ery wide plain

milling cutter is used.

ace "illing 4t is performed by a face milling cutter rotated about an axis perpendicular to the work piece.

Side "illing 4t is the operation of producing a flat #ertical surface on the side of work piece using a side

milling cutter.

,nd "illing 4t is the operation of a flat surface which may be horizontal& #ertical or inclined to the table. 4t

is also used for producing slots& groo#es and keyways.

$ng'lar "illing 4t is the operation of producing an angular surface on a work piece. (he angular groo#e

may be single or double angle.

*ang "illing 4t is the operation which in#ol#es the use of a combination of more than two cutters.

Saw "illing 4t is the operation of producing narrow slots or groo#es. %arting off operation can also be done

using the slitting saw.

T-Slot "illing 5 (+Slot is produced using a (+Slot cutter. (he (+slot milling cutter is a special form of end

mill.

orm milling 4t is the operation of producing the reAuired profiles on the work piece. (he profile may be

conca#e& con#ex or any other shape.

*ear C'tting (he gear cutting operation may be done using a form cutter& ha#ing formed ,utting edges of

in#olute shape.

=.2 Tool holding de%ices $r&ors 4t is a short shaft. (he cutters ha#ing a bore at the centre are mounted on

the arbor.

Collects 4t is used to hold straight shank milling cutters.

$da!tors 4t is used to hold& shank type cutters whose shank is smaller than that of hole in the spindle.

D.< "illing !rocesses



! milling 4t is also called ,on#entional Milling. 4t is the process of remo#ing metal by a milling cutter

rotated against the direction of tra#el of the work piece. (he cutting force in up milling increases from zero

to the maximum #alue per tooth mo#ement of the cutter.

own milling 4t is also called climb milling. Metal is remo#ed when the cutter teeth mo#e downwards.

'ere the cutter rotates in the same direction as the tra#el of the work piece.

1< *//* "$CH/,S

C.; *rinding 5 metal cutting operation performed by means of rotating abrasi#e wheel that acts as a cutting

tool called grinding. 5ccuracy in dimension is in the order of )> microns.

C.1=inds of *rinding:

o'gh or non !recision *rinding Snagging and off hand grinding are examples for rough grinding&

examples for this are trimming of surface left by the sprues and risers on castings& remo#al of flash on

forging etc.

+recision *rinding (his is connected with producing good surface finish and high degree of accuracy. (he

type of surface to be ground& is classified as

6a7 !xternal cylindrical grinding 6h7 4nternal ,ylindrical

6c7 Surface grinding 6d7 orm grinding

?.# *rinding machines

o'gh *rinders (he remo#al of stock without any reference to the accuracy. (hey are mainly of the

following type

6a7 Bench floor stand grinders 6b7 portable flexible shift grinders

6c7 Swing frame grinders 6d7 abrasi#e belt grinders

+recision grinders 5re those that finish parts to #ery accurate dimensions.

6a7 C(lindrical *rinders 4t is primarily used for grinding plain cylindrical parts& contoured ,ylinder& tapers

etc. (here are four mo#ements in#ol#ed in a cylindrical centre type grindingK

6i7 Fork must re#ol#e 6ii7 (he wheel must re#ol#e

6iii7(he work must mo#e past the wheel 6i#7 (he wheel must mo#e past the work.

* %lain center type grinders are essentially a lathe on which a grinding wheel has been substituted for a

single point tool.

* 4n uni#ersal centre type grinder& the head stock spindle can be swi#eled& at an angle in a horizontal plane.

6b7 Centreless grinders 4t is a method of grinding exterior cylindrical& tapered and formed surfaces on

work pieces that are not held and rotated on centers.

* 4t reAuires a grinding wheel& regulating or back up wheel and a work rest.

* ,entre less grinding may be done in one at three ways& through feed& inked& and end feed.

* (hrough feed is used for long and slender shafts& where no shoulders or other forms are not present.

* 4nfeed is used for components ha#ing forms or shoulders.



* !ndfeed is used for components to produce tapes components.

6c7 nternal grinders /sed to finish straight& tapered or formed holes to correct size. (here are three

general types of internal grinders.

6a7 ,hucking 6b7 %lanetary 6c7 ,entre less

S'rface grinder (hey are employed to finish plane or flat surfaces and also capable of grinding irregular&

cur#ed& tapered surfaces.Tool and c'tter grinder (hey are used mainly to sharpen and recondition multiple tooth cutters like

reamers& milling cutters& drills& taps etc.

6e7 S!ecial grinding machines (hese are used to do highly specialized work. !x + ,rank shaft grinders&

piston grinders& thread grinders and tool post grinders.

C.- 3heel "aterials

$&rasi%es 4t is a substance used for grinding and polishing operations. (hey are classified into two groups.

/at'ral 4ncludes sandstone or Auartz& emery& corundum diamond.

$rtificial 4nclude chiefly Silicon carbide and aluminum oxide.

?rit& ?rade and structure of grinding wheel

?rit or grain it indicate the size of abrasi#e grains used in making a wheel.

* ,oarse Fheels are used for fast remo#al of materials and for soft and ductile materials.

ine grain wheels are used to grind hard and brittle materials. .

*rade 4t refers to the hardness with which the band holds the cutting point.

(he grade shall be denoted by a alphabet. 5 to ' indicates soft grade& 4 to % indicates medium and R to I

indicates hard grain.

Structure of ?rain Spacing (he structure refers to the number of cutting edges per unit area of wheel face as

well as to the number size of #oid spaces between grains& denoted by numbers.

Soft and ductile materials reAuire an open structure.

'ard and brittle materials reAuire dense structure.

A.0 S'rface finishing o!erations

'oning 4t is a grinding process for finishing round holes by means of bonded abrasi#e stones hones.

* 5mount of material remo#ed is less ;.)> nun.

* 5utomobile cylindrical liners are honed for surface finish.

A.1 La!!ing 4t can be used on flat cylindrical and spherical surface.

* Metal that can be remo#ed is ;.;;> to ;.;1mm.

* 4t is used for slip gauges& piston pins& roller bearings and optical parts.

A.2 S'!er finishing ?enerally all machining and grinding lea#e surface with fragmented& metal which

cause excessi#e wear and noisy operations. 4t is remo#ed using super finishing.



* 5 #ery fine grit abrasi#e stone is used.

* 5mount of material remo#ed is around about ;.;;> mm.

A.5 B'ffing 4t is a final operation to remo#e the polish of a metal and to bring maximum luster.

* %olishing wheels with fine abrasi#e particles are used.

+ickling 4t refers to the remo#al of surface oxides and scale from by acid solutions.

,ommonly pickling solutions contain sulphuric or hydrochloric acids.

4t is commonly done on rolled shapes& wires& sheets heat treatment steel parts.

* 4n some applications& such as on aluminum& pickling is called oxidizing.

A.> ,lectro +lating 4t is the most popular means of applying metallic coatings on the surface of metals and

sometimes on non+metals.

* (his is done for protection against corrosion or against wear and abrasion and for appearance.

* (he four ,ommon plating metals are chromium& nickel& copper& zinc& and tin.

* (he four essential elements of a plating process are the cathode& anode& electrolyte and direct current.

A.D Hot i!!ing +. 5 protecti#e coating may be applied on by dipping them into certain molten metal

namely zinc& tin or an alloy of lead and tin.

* (he process of zinc coating on steel is called gal#anizing.

*ear c'tting ?ears can be best produce on mass production by hobbing.

* ?ear finishing operation is called gear sha#ing. .

* (hin gears from sheet metal can be produced commercially by stamping.

* ?ear bobbing process is faster than milling because se#eral teeth cut at time. .

L$3S O "OTO/

1.; "echanics 4t is the branch of %hysics which deals with action of forces.

9inematics deals with motion of bodies and not about magnitude of forces.

ynamics is the mathematical and physical study of the beha#ior of bodies under the action of forces that

produce motion in a body.

Statics is the mathematical and physical study of the bodies in eAuilibrium under the action of forces.

1.1 =inematics

isplacement is the shortest distance between initial and final position of the particle.

* Speed is the ratio of the distance tra#elled to time. 4t is a scalar Auantity.

(he displacement of a body in unit time is called #elocity.



* 5 mo#ing particle is said to ha#e uniform #elocity when eAual displacement of particle takes place in eAual

inter#als of time.

* Fhen n a body mo#es with uniform #elocity& its acceleration is zero.

* (he negati#e acceleration of a body is called 0etardation.

1.) ,)'ations of motion 5 body mo#ing with uniform acceleration "a". $et its initial #elocity be PuO and

attains a #elocity "". after co#ering a distance "sO in the time "tO.

$inear motion # u at K S ut 1

2 at) K #)+ u) ) as K Sn u 6n + 1D)7 a

"Sn" is the distance co#ered by the body in PnO th second.

ertical motion # u T gt K hut T1

2 gt) K #) U u) ) gh

,ircular motion & ω ω

1+αt

Kθ=ω

1t +

1

2α t

2

K ω2

2−ω1

2=2αθ

Fhere ω angular #elocity 6radDs7K Q angular acceleration 6radDs)7 K θ angular displacement 6rad7

Maximum height reached by the #ertically thrown body "'O U

2

2 g

(ime of ascent is the time taken to reach the height by the bodyPtO U

g

(ime of descent is the time taken to tra#el from highest point to the position from which it has pro3ected

upwards. t U

g

(ime of flight of a body is sum of time of ascent and time of descent. ( 2U

g

1.2 "otion in two dimensions

+ro7ectile 5 body which mo#es in a two dimension plane in the gra#itational field of earth is called a

pro3ectile.



Tra7ector(: (he path followed by the pro3ectile is called tra3ectory. (he path of tra3ectory parabola.

* (ime of flight 6(7 2U sin θ

g

Fhere " θ O is angle of pro3ectionK "u" is initial #elocity.

ange ;: (he horizontal displacement undergone by a pro3ectile& when it returns to its initial ele#ation.

0U

2

sin 2θ

g

"a8im'm height (he maximum height of a pro3ectile is reached at a time when its #ertical #elocity

component has decreased to zero.

'U

2sin

2θ

2g

4n long 3ump& the maximum span of 3ump is obtained when the angle of take off is 2><.

1.5 "ass 4t is the amount of matter contained in a gi#en body. 4t does not #ary with the change in its

position on the earth surface. 4t can be measured by Balance le#er.

1.< 3eight 4t is the gra#itational force of attention of the body towards the centre of earth. 4t #aries with

place to place. Feight is measured by spring balance.

).; /ewtonEs law of motion

/ewtonEs first law (he momentum of body remains as along as no external force acts on it.

* irst law introduces the concepts of "force and inertia" and leads their definitions.

orce orce is that which changes or tends to change the state of rest or of uniform motion of a body.

nertia 4nertia is the inability of a body to change its state.

/ewtonEs Second law 0ate of change of momentum is directly proportional to applied force.

ma&

/nits S. 4 V Eewtons ,.?.SVdynes M.9.SVkgmDs).

/ewtonEs Third law (o e#ery action there is an eAual and opposite reaction.

m!'lse 4s the product of force and time of application of force .

4mpulse 4t 647 x tm 6 + u7 L

/nits ,.?.S → dyne+sec S4 VEs



).1 Law of conser%ation of moment'm Fhen no external force acts on a system& the algebraic sum of the

momentum of the bodies in the system remains constant any direction after any number of collisions.

m1 u1 m) u) m1 #1 m) #)

u1 u) #elocities of bodies before collision #1 #) are #elocities after collision.

* 4f second body is mo#ing in opposite direction to first one before collision.

m1 u1 + m) u) m1 #1 m) #)

Jet planes and 0ockets work on the principle of conser#ation of momentum 6or7 Eewton"s third law of

motion.

0ecoil of a gun is due to the principle of conser#ation of momentum 6or7 Eewton"s third law of motion.

).) Law of conser%ation of energ( 5ccording le law of conser#ation of energy& energy can be neither be

created nor be destroyed& it ,an be transferred from one form to another form.

Mechanical energy is con#erted into electrical energy by a dynamo.

!lectrical energy is con#ened into heat energy is con#ened into heat energy and light energy by arc lights&

electric bulbs and heaters.

Sound energy is con#erted into electrical energy by microphones.

4nternal combustion engines con#ert chemical or heat energy into mechanical energy.

* Fater falling from a certain height con#erts %.!. into 9inetic energy.

* Battery con#erts chemical energy into electrical energy.

* Steam engine con#erts heat energy into mechanical energy.

* %elton wheel con#erts potential energy into mechanical energy.

* !lectrical motor con#erts electrical energy into mechanical energy.

2.0 otational motion

5 body is said to ha#e rotate. Motion when it mo#es in a circular path about a fixed point or about an axis.

!g (he motion of a grinding wheel& a fly wheel and the rotary motion of the earth about its own axis.

(he angle subtended by an arc of length eAual to its radius& at its centre is called radian. 8ne radian is eAual

to >=<.1C"

* (he rate of angular displacement of a body is called #elocity 6 ω 7.

∗ $inear #elocity is the product of angular #elocity 6 ω 7 and radius of the path 6r7 i.e.& r ω .

5ngular acceleration 6Q7 is the rate of change of angular #elocity.

∗ ,entripetal acceleration of a particle in circular motion with constant speed "#O isv2

r directed

towards the centre.



∗ (he centripetal force is that force& which acting at right angles to the motion of the body causes it to

mo#e in a circular path with constant angular #elocity. (his force is needed to keep a body in circular

motion.

∗ (he gra#itational force applied by the sun on the earth makes re#ol#e round the Sun. (his radial

force& directed towards the centre of the earth"s force& is centripetal force.

∗ (he force experienced by a body mo#ing in a circular path radially outwards is called the centrifugal

force.

∗ Separation of cream by skimming milk& centrifugal pump basing on centrifugal∗ (orAue is the product of force and perpendicular distance of the point from the line of action of the

force 6( f x r7

∗ 4n rotatory motion& moment of a force or (orAue is the product of moment of inertia 647 and angular

acceleration 6 Q7

∗ %ower 6%7 is the product of torAue 6(7 and angular #elocity 6 ω

7.

∗ 4n general& most of bodies like motion of the earth& ha#e both translatory and rotatory motions. (he

total kinetic energy is the sum of its translatory and rotational kinetic energies.

(otal 9.! 1

2 m#) 1

2 4 w)

(he angular #elocity of seconds hand of watch is π D-; radDsec.

5.0 $!!arent weight of a !erson in a lift

* w mg is the real weight of a person.

* 4f the lift mo#es up with constant acceleration 6a7 the apparent weight of the person F 1 m 6g a7

∗ if the lift mo#es down with a constant acceleration F) m 6g+a7

• 4f the lift mo#es up or down with uniform acceleration F- mg

∗ 4n the case of a freely falling lift& the apparent weight of the person is zero.

<.0 3orkF +ower and energ(

Fork is the product of force and displacement measured in the direction of force.

F . S. ,os θ

/nits ,.?.S system !rg S 4 system Joules& 1 Joule 1;) erg

∗ 8ne kilo Fatt hour 69wh7 or unit is eAual to -: x 1;> 3oules.

∗ %ower is the time rate at which work is done.

% FDt& /nits ,.?.S System ergDsec& S.4 System 3DS 6or7FattD

* !nergy is the capacity to do workK it has the same units as work.

∗ Mechanical energy is of two forms& potential energy and kinetic energy.

∗ %otential energy is the energy possessed by a body by #irtue of its position&

%. ! mgh

4



∗ 9inetic energy is the energy possessed by #irtue of its motion& 9. ! 1

2 m#)

(he relation between momentum and energy is & 9.! P

2

2m where PpO is the momentum of body.

∗ (wo bodies of different masses ha#e the same kinetic energy. Fhen hea#ier mass has greater momentum

than the lighter mass.

>.0 imensional form'la-:

Force : MLT −2

Momentum and Impulse : M.LT -1

Power : M L2T -3 Work and energy : ML2T -2

ngular !eloc"ty : T

-1

ngular accelerat"on : T

-2

#tress : M L-1 T -2 #ur$ace tens"on : ML-2

%"scos"ty : ML-1 T -1 Latent &eat : L2 T -2

'lectr"c c(arge : T Moment o$ Inert"a : M L2

)ra!"tat"on constant : M -1 L3 T 2 Pressure : ML-1T 2

*oung+s, modulus : ML-1T -2 #pec"$"c (eat : L2 T 2 -1

Vectors and Scalars

Vector 5 physical Auantity which has magnitude and direction is called #etor. !.g. isplacement& #elocity&

momentum and force.

Scalar 5 physical Auantity which has only magnitude is called Scalar. !g. Mass& time& speed& energy&

#olume& density and work.

?.0 riction

∗ riction (he force which always opposes the motion of one body o#er there body in contact with it is

called the friction.∗ Static friction (he maximum frictional force present when a body 3ust tends to slide o#er the surface of

another body is called the static friction.

• (namic friction (he frictional force present when one body slides o#er other body are known as dynamic

friction or kinetic friction.

0olling friction Fhen a body like a wheel& cylinder& or drum rolls o#er the. Surface of another body the

friction is called roiling friction

?.#. Coefficient of friction

* (he ,oefficient of friction between two surfaces is the ratio of the frictional force to the normal reaction. W

D0

Fhere "XO is the ,oefficient of friction. "O is the frictional force. "0" is the Eormal reaction.

Xs Y Xk YXr K Xs is the coefficient of static frictionK



Xk is the coefficient of kinetic reaction&

Xr is the coefficient of rolling friction.

$ngle of friction 4ncase of limiting friction& if the normal reaction and the frictional force be compounded

into a single force& which is referred to as resultant. (he angle which this resultant makes with the normal

reaction is called the angle of friction.

(an θ D0

?.5 The laws of limiting friction:

∗ riction always opposes motion.

∗ (he force of friction is proportional to the normal reaction between the two surfaces in contact.

∗ riction is independent of the areas of the surfaces in contact& but depends on the material& nature and

condition of the surfaces in contact.

A.0 +lanetar( motion

Laws of 'ni%ersal gra%itation (he gra#itational force of attraction between two bodies is directly

proportional to the product of their masses and in#ersely proportional to the sAuare of the distance between

their centres.

Q

m1

m2

r2 or Q

G m1

m2

r2

Fhere "?" is the uni#ersal gra#itational constant.

? :.:= x 1;+2 dyne U cm) gm+) in ,.?.S system.

:.:= x 1;Z+11 Eewton U m) kg+) in S. 4. system.

?M

0elation between "?" and "g" is g

GM

R2

10.0 Sim!le harmonic motion

5 body is said to ha#e simple harmonic motion& if its acceleration is always directed towards a fixed point onits path and is proportional to its displacement from the fixed point.

(he maximum displacement of the #ibrating particle on either side of the mean position is called its

amplitude.



+eriod of Oscillation 6t7 (he time for one complete 8scillation of the particle is called period of 8scillation

or #ibration.

( 2 π

W =2π √

displacement

accleration √ y

a

re)'enc( n7 (he number of #ibrations made by the particle in unit time is called freAuency

E 1

T =

W

2π =

1

2π √ a

y K /nit hertz 6'z7

* Sim!le +end'l'm (he period of a simple pendulum is directly proportional to the sAuare root of its length

() π √ L

g or g 2 [) 6

L

T 2 ¿

T$/S"SSO/

1.; * in transmission of power& mechanical& electrical& hydraulic and pneumatic dri#en are employed. Belts&

ropes& chain dri#es and gears are examples of mechanical dri#es.

1.1 Belt and ro!e dri%es

∗ Belts or ropes are used to transmit power from one shaft to another by means of pulleys.

∗ Belts are made of leather& rubber& cotton& balata& fabric.

1.) T(!es of Belts 5ccording to the speed of the dri#e belts classified into the following three groups.

6a7 Light dri%es (hese are used to transmit small powers at belt speed up to about 1; mDs& as in agricultural

machines and small machines tools.

6h7"edi'm dri%es (hese are used to transmit medium power at belt speeds o#er 1; mDs but up to )) mDs& as

in machine tools.

6c7 Hea%( dri%es (hese are used to transmit large powers at belt speeds abo#e )) mDs& as in compressors and

generators.

∗ 5ccording to the shape& belts are classified into three types.

6a7 lat belts 6b7 +belts 6c7 ,ircular belts or ropes

1.- lat Belts (hese are used to transmit power& from one pulley to another when the two pulleys are not

more than C meter apart.

(he standard flat belt thicknesses are >& :.>& C& 1; and 1) mm.



1.2 t(!es of flat &elt dri%es

O!en &elt dri%e

∗ 4t is used for shafts arranged in parallel and rotating in the same direction.

∗ 5ngle of contact is less in these belts& when compared with cross belts.

∗ $ength of the open belt 6$7 is gi#en by& $π

2 6d1 d) 7) (d1−d2)

2

4

Fhere d1 d) are diameters of larger and smaller pulleys. P O is the centre to centre distance between pulleys.

∗ elocity ratio of open belt dri#e eAual to the in#erse ratio& of pulley diameters

N 2

N 1=

d1

d2 or

d

(¿¿ 2+1)(d

1+1)¿

Fhere PtO is the thickness of the belt.

∗ 4n case of compound belt dri#e& the #elocity ratio is

0 !peed o" # Last "ollo$er

!peed o" "irst driver =

Prod%ct o" diameter o" drivers#

Prod%ct o" diameter o" "ollo$ers#

* 0elati#e motions the belt and the pulley surface is called slick. 4t reduces the #elocity ratio.

N 2

N 1=

d1

d2

(1− s

100) where PsO is the total percentage of slip.

Cross &elt dri%e

* 4t is used with shafts arranged in parallel but rotating in opposite directions.

* Fear and tear in a cross belt is higher due to rubbing at the crossing+point.

* $ength of the cross belt dri#e

$ π

2 6d1 d) 7 ) /(d1+d2)

2

4

* $ngle of contact is more.

Ruarter turn belt dri#e 4t is used with shifts arranged at right angles and rotating in one definite direction.



Ste!!ed or cone !'lle( dri%e:

* /sed for obtaining different speeds on the dri#e shaft with a constant speed dri#er shaft.

* (his is done by shifting the belt from one step to the other on the stepped cone pulley.

ast and loose pulleys (here will be two pulleys on the dri#en shaft. 8ne keyed to the shaft and the other

freely rotating relati#e to the shaft.

* 4t is used when the dri#en or machine shaft is to be started or stopped when e#er desired without interferingwith the dri#ing shaft. (his is done by shifting the belt froth the loose pulley to the fast pulley or #ice+#ersa.

Crowning %ulleys are pro#ided with con#ex rims to a#oid running away of belts. (his con#exing is known

as crowning.

1.< +ower Transmitted &( a Belt: %ower transmitted by a belt 6(1 U()7 watts where

(1 (ension in the tight side in Eewton () (ension in the slack side in Eewton& and

elocity of the belt in mDs.

%ower transmitted

T 1−T

2

75 h.p.

Fhere (1 and () are in kgf.

1.> Cree! ue to the difference of two tensions& the belt continuously mo#es with a #ery negligible #elocity

o#er the pulleys.

4t is called as ,reep.

(ight side and Slack side (he lower side of a running belt is known as tight side and upper side of the belt is

known as slack side.

0atio of dri#ing tension for flat beltsT 1T 2

=e &θ

Fhere (1 and () are the belt tensions on tight and slack sides.

" θ O is angle of contact in radians.

1.D Centrif'gal Tension ,entrifugal tension 6(c 7 m#)

∗ ,entrifugal tension is independent of the belt tensions. (1 and () depend on belt #elocity and belt density

only.



* (he power transmitted by a belt dri#e is maximum when the maximum tension in the belt is three times the

,entrifugal tension (max - (c

1.? nitial tension To ; in the Belt

∗ 4nitial (ension 6(o 7 in the belt is gi#en by& (o 6(1 () 7 D)

* Fhen centrifugal tension is taken into account (o

T 1+T

2+2T c

2

V-&elts

* 5 #+belt is made of fabric and cords usually cotton& rayon or nylon and impregnated with rubber.

* +Belt are used for smaller centre to centre distance between shafts.

* + belts are made endless and there is no 3oint trouble& therefore the dri#e is smooth.

* +Belt is of trapezoidal cross section the included angle #aries between -;< to 2;.

* (he rim of the pulley is groo#ed in which the belt runs. (he +belt is contact with sides of the groo#e and

not the bottom to gi#e good grip and also to ad3ust automatically as the belt wears.

* +belts may be operated in either direction& and high #elocity ratio is obtained.

* (hese are use to transmit #ery large amount of powers.

* Slip is negligible and hence it is a positi#e dri#e.

* $ength of the belt 6$7 is gi#en by the same eAuation used for a flat open belt.

0atio of dri#ing tension is gi#en by T 1T 2 eX\ cosec] K where P]" is the semi groo#e angle&

#.0 o!e dri%es

(he ropes dri#es are widely used where a large amount of power is to transmitted from are pulley to another&

o#er a considerable distance.

* (he ropes dri#es use the following two types of ropes 6a7 fiber ropes& and 6b7 wire ropes.

(he groo#e angle of the pulley for rope dri#e is usually 2><.

(he ratio of dri#ing tensions for fiber rope

T 1

T 2 eX\ cosec] where "] "



* (he fiber ropes operate successfully when the pulleys are about :; meters apart& while the wire ropes one

used when the pulleys are upto 1>; meters apart.

∗ Fire ropes run on groo#ed pulleys but they rest on the bottom of the groo#es and are not wedged

between the sides.

2.0 Chain dri%es

,hain dri#es are used to transmit large power where the distance between two rollers or sprockets is small.

,hain dri#es gi#e a constant #elocity ratio.

* Eo slip or creep is in#ol#ed.

,hain dri#e is a positi#e dri#e.

(he chain runs o#er sprockets with ha#e teeth on the circumference.

(he 0elation between pitch and pitch circle diameter is

(1 and () are number of teeth on the sprockets

^x" is the centre to centre distance.

∗or smooth operation it is good practice to use minimum 1= teeth on the dri#ing sprocket.

∗%ower transmitted 6p7 is gi#en by& % ' ()

60 watt

dri#ing force elocity of chain in mDmin.

Bush and roller chains are used in motor cycles and cycles.

5.0 *ears:

∗?ears are mainly used to transmit larger powers for smaller distance.

∗(hey will transmit exact #elocity ratio.

∗(hey may be used to change the speed or the torAue of one shaft with relation to another.

5.1 T(!es of *ears:

S!'r *ears:



Spur gears are used to transmit power between two shafts which are parallel and coplanar. (he larger wheel is

called spur wheel and smaller pinion.

!.g. $athe machine.

Helical *ears these are also used for the same purpose as the spur gears are used& put the teeth cut on the

gears are inclined at an angle ranges from );< to -><.* /sed to transmit power between parallel shafts and shafts are inclined at any angle but not intersecting.

Be%el gears (hese are used to transmit power between taco shafts whose axes are perpendicular to each

other. !.g. + rilling Machine.

S!iral gears (hese are used when the axes of the shafts are non+intersecting and non parallel.

3orm and 3orm 3heels (hese are used in the same manner as spiral gears are used but instead of a

pinion a shaft ha#ing thread on its periphery is used to transmit motion or power.

* 5 high speed reduction ratio is possible.

ack and +inion 5 rack is a gear with an infinite radius& or a gear with its perimeter stretched out into a

straight line.

* 4t is used to change reciprocating motion to rotary motion or #ice #ersa.

H(!oid gears 'ypoid gears are similar to be#el gears& but the shafts do not intersect.

2.# terms 'sed in n gears

+itch Circle 4t is an imaginary circle which by pure rolling action& would gi#e the same motion as the actual

gear.

+itch Circle diameter 4t is the diameter of the pitch circle. (he size of the gear is usually specified by the

pitch circle diameter. 4t is also called as pitch diameter.

$ddend'm 4t is the radial distance of a tooth from the pitch circle to the top of the tooth.

edend'rn 4t is the radial distance of a tooth from the pitch circle to the bottom of the tooth.

Circ'lar +itch 4t is the distance measured on the circumference of the pitch circle from a point of one tooth

to the corresponding point on the next tooth.

%c

πD

T & where iameter of the pitch circleK ( Eo. of teeths



iameteral +itch 4t is the ratio of number of teeth to the pitch circle diameter in millimeters. 4t is denoted

by %d

iametral pitch %d

T

D=

π

Pc

"od'le 4t is the ratio of the pitch circle diameter in millimeters to the number of teeth. 4t is usually denoted

by "m.

Module m D

T

Velocit( ratio 4f 1 and ) are pitch circle diameters of dri#er dri#en ha#ing teeth ( 1& and () respecti#ely&

then #elocity ratio

D2

D1

=T

2

T 1

Backlash 4t is the difference between the tooth space and the tooth thickness& as measured on the pitch

circle.

<.0 Bearings

<.1 5 bearing is a machine element which supports another mo#ing machine element. 4t permits a relati#e

motion between the contact surfaces of the members& while carrying the load.

<Classification of Bearing

* epending upon the direction of load to be supported

(he bearings under this group are classified as

6a; adial &earings (he lead acts perpendicular to the direction of motion of the mo#ing element.

6b7 thr'st &earings (he load acts along the axis of rotation.

* epending upon the nature of contact (he bearings under this group are classified as.

6a7Sliding contact bearings 6b7 rolling contact bearings

Sliding Contact Bearings (he sliding takes place along the surfaces of contact between the mo#ing element

and the fixed element.

* (he sliding bearings in which the sliding action is along the circumference of a circle or an arc of a circle

and carrying radial loads are known as Journal or Slee#e bearings.

Self lubricating bearings are the bearings which need no lubrication during their span of ser#ice.



*thrust bearings are classified as 6i7 %i#ot or foot Step bearings 6ii7 ,ollar bearings

olling contact &earings

* 4n rolling contact bearings& the contact between the bearing surface is rolling instead of sliding& ha#ing

point or line contact between the contact surfaces

ue to low friction offered by rolling contact bearings& these are called anti friction bearings.

0olling contact bearings are classified as 6a7 ball bearings 6b7 roller bearings

* Ball bearings will ha#e balls as rolling members and they ha#e point contact with surfaces.

* 0oller bearings will ha#e rollers as rolling members and they ha#e line contact surface.

S"+L, "$CH/,

1.; "achine 5 machine is a de#ice used to recei#e energy in some form and con#ert it into some useful

work.

1.1 Sim!le "achines Simple machine is a de#ice /sed to lift hea#ier loads by exerting smaller efforts.

!.g.& $e#er& inclined planes& pulleys& wheel and axle& screw 3ack etc.&

1.) in!'t of "achine (he work done on the machine by the effort is known as input of machine.4t is the product of effort and distance mo#ed by the effort.

4nput of the machine % x N

1.- O't!'t of "achine (he actual+work done by the machine in lifting the load is called output of a

machine. 4t is eAual to the product of the load and the distance mo#ed by the load.

8utput of the machine F x _

1.2 Velocit( atio 4t is the ratio of distance mo#ed by the effort to the distance mo#ed by the load in a gi#en

time is called the #elocity ratio.

elocity 0atio 6.07 distancemoved *y t+e e""ort

distancemoved *y t+e load ,

-

1.> "echanical $d%antage (he ratio of load 6w7 to effort 6p7 is called mechanical ad#antage

Mechanical 5d#antage 6M57 Load

.""ort W

P

1.: ,fficienc( of a "achine 4t is defined as the ratio of work done by the machine to the energy supplied to

machine.

/=0%tp%t

1np%t =

W

Py =

M # 2

) # R

Fhere x distance mo#ed by load y distance mo#ed by effort



1.= deal machine 4f there is no friction in the machine& then the output of a machine is eAual to the

input.Such machine is called as an 4deal rnachine.

/= M # 2

) # R =1

(he efficiency of 4deal machine is 1;;<T1=

1.C e%ersi&le and rre%ersi&le "achine 5 machine is said to be a re#ersible machine& if it is capable of

doing the work in re#erse direction after the effort is remo#ed. (he efficiency should be more than >;G.

∗ 5 machine that is not capable of doing any work in the re#erse direction after the effort is remo#ed is

called a self+locking 6or7 4rre#ersible machine& for self locking machine its efficiency should not be

more than >;G.

1.@ Law of "achine 4t gi#es the relationship between the load lifted and the effort applied. 4t is gi#en by %

mw c

Fhere "c" is the minimum effort reAuired to operate the machine and is eAual to the frictional effort.

∗ or 4deal machine , is eAual to zero.

∗ 4deal machine M5 is eAual to 1Dm and maximum efficiency of lifting machine is1

m )R

).; Le%ers 5 le#er is rigid bar capable of rotating about a fixed point is called fulcrum. (he purpose of le#er

is to left hea#ier loads by applying a smaller effort.

).1 T(!es of le%ers: $e#ers are three kinds.

∗ 5 le#er of the first kind or class consists of a fulcrum which is situated between the Feight and effort.

∗ M.5 can be less than& eAual to& or more than 1.; for a first+order le#er.∗ !xamples of first order le#er crow bar& scissors& beam of ,ommon balance& cutting pliers& see+saw etc.

∗ 5 le#er of the second kind consists of a weight situated in between the fulcrum and the effort.

∗ 4n second class le#er effort arm is more than load arm. M 5 is always greater than one.

∗ !xample of second order le#er is Eut cracker& wheel barrow& lemon sAueezer& foot bellows& punching

machine etc.

∗ 5 le#er of the third kind consists of an effort situated in between the fulcrum and the weight

∗ in third class le#er load arm is more than effort arm. M5 is always less than one.

∗ !xamples for third order le#er are& 'uman fore arm& fire tongs& nail cutter& forceps& stapler etc.&

-.; nclined +lane: 5n inclined plane is a smooth plane inclined at a certain angle " θ " with the horizontal.

∗ effort is parallel to plane M.5 1

sinθ * (he effort is parallel to base M.5 1

tanθ

2.; elocity ratio of a few simple machines

∗ Simple wheel and axle& 0 D

d "" is dia. of wheel& d+ dia. of axle.

∗ Fheel and differential axles& 0 2 D

d1−d

2 d1 dia. of bigger axle& d) dia. of smaller axle.

∗ 4 system of pulleysK 0 )n n no. of mo#ing pulleys.

∗ 44 system of pulleys K 0 n



∗ 444 system of pulleys 0 )n+1 ∗Form and+ worm wheel 0 l3

r n

l $ength of effort handle& r radius of load drum& z no. of teeth on worm wheel& n multiplicity of threa

∗ Screw Jack 0 2 πL

l

$ $ength of effort handle& $ np lead of screw& n thread multiplicity& p pitch of threads

∗ 0ack and pinionK 0 2 πL

4P % %itch& 4 length of handle& I no of teeth on pinion

>.; Screw 6ack Screw Jack works on the principle of inclined plane. 4t is used to lift the #ehicles up for

repairs and also for change of tyres and to lift hea#y loads.

∗ (he screw threads follow a helix with helix angle Q. 'elix angle tan Q %D[d

∗ !ffort 6p7 reAuired to lift a load 6w7 is gi#en by % F (an 6Q 7& where is angle of friction.ϕ ϕ

∗ efficiency of the screw 3ack is ` tan∝

tan (α +ϕ )

∗ (he maximum efficiency of a screw 3ack is gi#en by `max 1−sin∅

1+sin∅

∗ !fficiency of a screw 3ack is independent of the load lifted or the effort applied.

∗ Screw 3ack is a self locking machine and sAuare thread is used in a screw 3ack.

,*,$TO/ $/ $ CO/TO//*

1.; efrigeration 4t is the process of remo#ing heat from a body and maintaining the temperature of body

is lower than that of its surroundings.

1.1 Heat !'m! 4t is a machine& which extracts heat from a cold body deli#ers it to a hot body.

efrigerator 4t is a storage chamber& in which the heat pump works and keeps it cool.

1.) efrigerant 4t is a substance which works in a heat pump to extract heat from a cold body and to deli#er

it to a hot body.

1.- Ca!acit( of refrigerator: 4t is the rate at which heat can extracted from the cold body. (his rate is

expressed in tonne of refrigeration.

1.2 nits of efrigeration 5 tonne of refrigeration is eAual to the amount of refrigeration produced by the

melting of 1 tonne of ice in )2 hours.

∗ Fhen one tonne i.e. 1;;; kg ice melts )2 hours& it produces a cooling effect at the rate of )1; 9JDmin or >;

calDmin.

1.> Coefficient of !erformance (he ,oefficient of performance 6,.8.%7 is the ratio of heat extracted in the

refrigerator to the work done on the refrigerant.



,8% 5eat .tracted

Wor6 done 0elati#e ,8% 2ct%al70P

T +eoritical70P

• (he coefficient of performance is the reciprocal of the efficiency of a heat engine.

(he #alue of ,.8.% is always greater than unity.

).; "ethods of efrigeration:

).1 r(- ce efrigeration Solid carbon dioxide is known as dry ice. 4t can be pressed into thin slabs or

flakes. ry ice absorbs heat if flakes are placed in a container during transportation o#er a long period.

).) $ir efrigeration: (his method in#ol#es compression and subseAuent expansion of air. (high pressure is

allowed to expand adiabatically its temperature falls. (he cool air is circulated in a cold chamber to remo#e

the heat of products placed in it.

∗ 5ir refrigeration system is largely used in air conditioning system of air craftOs.

∗ 5ir refrigeration system works on re#erted Joule"s cycle or Bell ,oleman cycle.

∗

5ir refrigeration has limited used because of low ,.8.% and bulky eAuipment.

).- Va!o'r Com!ression efrigeration S(stem: 4t is a type of a mechanical refrigeration system in which a

suitable working substance& termed as refrigerant is used.

∗ (he refrigerant used& does not lea#e the system& but is circulated throughout the system alternately

condensing and e#aporating.

∗ apour ,ompression refrigeration system consists of four basic components namely ,ompressor&

,ondenser& !xpansion al#e and e#aporator.

∗ O!eration of Va!o'r Com!ression efrigeration S(stem

Com!ression !rocess .(he dry state #apour at a low pressure is sucked from the e#aporator during thesuction stroke of the compressor than the #apour is compressed to higher pressure and temperature.

Condensation !rocess (he #apour under high pressure is deli#ered to the condenser. (he #apour is

condensed into liAuid form in the condenser using cooling medium such as water.

Throttling +rocess high pressure liAuid is expanded to e#aporator pressure through a throttle #al#e.

,%a!oration +rocess (he wet #apour of throttling passes through e#aporator coils and absorbs heat from

products and gets e#aporated.

The condition of refrigerant in a c(cle:

Before ,ompressor → $ow pressure dry saturated #apour

5fter ,ompressor → high pressure high temperature #apour

5fter ,ondenser → high pressure liAuid

5fter !xpansion → #al#e low pressure wet #apour

∗ (he highest temperature occurs at compressor discharge.

∗ (he lowest temperature occurs after !xpansion al#e.

∗ 4n #apour compression refrigeration system& the refrigerant re3ects heat in condenser.

∗ 5ccumulator is placed in apour ,ompression refrigeration system between !#aporator and ,ompressor.

∗ 5ccumulator is a de#ice that drops liAuid particles if present in #apour refrigerant lea#ing the e#aporator.



∗ (he moisture in a refrigerant is remo#ed by driers.

∗ rier is installed between condenser and !xpansion #al#e. riers are also ,alled ehydrates.

∗ 5 flash chamber is used in between the expansion #al#e and e#aporator" td remo#e the flashed refrigerant&

∗ Strainers are used to remo#e any foreign Matter from refrigerant.

∗ !#aporati#e condensers are used when the water supply is limited. !.g. 4ce plants& theatre air conditioning etc

∗ !xpansion de#ices+are used to regulate the flow of refrigerant.

).2 apour absorption 0efrigeration System (he idea of a #apour absorption refrigerator is to a#oid

compression of the refrigerant.

∗ 5 #apour absorption refrigeration system consists of e#aporator& absorber& generator& condenser&

!xpansion #al#e and a pump.

∗ 4n a #apour absorption system two working fluids are employed& a refrigerant and an absorbent.

∗ Most commonly 5mmonia is used as refrigerant and water as absorbent 4t is also known as .aAua+

ammonia.

∗ (he system is Auiet in operation since absence of compressor.

∗ !nergy input generator is mainly heat which is a low grade energy&

#.2- ,lectrol'8 refrigerator:

∗ (here are no mo#ing parts in !lectrolux system. (he pump may be omitted by the introduction of

hydrogen into the low pressure side.

∗ (he !lectrolux refrigerator works on three fluids& 617 ammonia as a refrigerant 6ii7 Fater as an absorbent

and 6iii7 'ydrogen as a pumping agent.

2.0 efrigerants:

*5 refrigerant is any substance which acts as a cooling agent by absorbing heat from another substance. 4t isa working agent employed in a refrigeration system.

2.1 +ro!erties of a refrigerant: 5n 4deal refrigerant should ha#e the following properties.

* $ow boiling and low freezing point. * Stable o#er a wide range of pressures and temperatures.

*'eight latent heat of #apourisation. ∗" Eon toxic& Eon flammable and non explosi#e.

∗ Eon ,orrosi#e to metal. * $ow+specific heat in liAuid state.

0efrigerants are classified into 6a7 %rimary 0efrigerants 6b7 Secondary 0efrigerants

+rimar( efrigerant 4t is that which cools the substance by absorbing heat eAual to its latent heat from

them.

D1D $mmonia /H;

∗ Boiling point 6B%7 is +--< , and freezing point is + =C< ,

∗ (oxic& slightly explosi#e and inflammable&

∗ 5mmonia should be used with Steel pipes and ne#er with copper& Brass or their alloys.

∗ !xtensi#ely used in cold storages& ice plants& food refrigeration plants etc..

D55 Car&on dio8ide 6,8)7

∗ Boiling point is + =C< , and freezing point is + >=<,.

∗ ,olourless& non+to and non+flammable.



∗ Eon explosi#e and non+corrosi#e.

∗ /sed in marine application and as dry ice.

∗ hea#ier working parts needed becaute of high+ operating pressure

D>5 S'l!h'rdio8ide 6S8)7

* Boiling point is + 1;<+, and+freezing point is + =>.>< ,..

* Eon+flammable& non explosi#e and highly toxic .

* Forks at low pressures.

-11 freon 11; Trichloro fl'oro "ethane CCl2;

* Boiling point is + )2< , and freezing point is +111< ,.

* non toxic& non+flammable+and non+corrosi#e.

∗ 4t is used with centrifugal compressors.

∗ 4t is used in >; tonnes capacity air conditioning plants.

- 1# freon - 1#; ichloro ifl'ro methane C Cl# #;

∗ Boiling point is + -;< , and freezing point is + 1>C<,.

∗ Eon+toxic& non+flammable and non+explosi#e.

∗ /sed in domestic applications and water coolers.

∗ it is corrosi#e to magnesium or aluminum.

- ## freon-##; Chlorodifl'oro "ethane CH Cl# #;

∗ Boiling point is + 2;.=:< , and freezing point is + 1:.;< ,

• /sed with reciprocating compressor in large units such as package units and central air conditioning

plants.

5zerotropes

∗ (hese are the mixtures of different halocarbons which beha#e like a compound.

∗ 0+>;; is a mixture of =-.CG of 0+1) and ):.)G of 0+1>).

* 0+>;1 is a mixture of 0+)) and 0+1) 6=>G )>G7

0=)@5ir

∗ Boiling point is + 1@2< , and critical temperature is + 12;< ,

∗ 'armless& freely+a#ailable.

∗ !Auipment becomes bulky..

-.; $ir Conditioning:

5ir conditioning is defined as the simultaneous control of temperature& humidity& air circulation and

cleanliness of air within an enclosed space.

+s(chrometer %sychrometer is the stud of properties of mixture of air and water #apour. 4t is also called

'ygrometer.



r( $ir ry 5ir is a mechanical mixture of constituent gases which comprise atmospheric air excluding

water #apour.

"oist $ir Moist air is a mixture of dry air and water #apour. Fater #apour in air is "usually called moisture.

H'midit( (he water #apour that is contained in or mixed with atmospheric air is the humidity.

elati%e H'midit(+ it is the ratio of mass of water #apour in a gi#en #olume of air to the mass of water

#apour reAuired to saturate the same #olume of air at the same temperature.$&sol'te H'midit( 5bsolute humidity is the amount of water #apour present per unit #olume of air.

r( &'l& Tem!erat're 6T7 4t is the temperature indicated by ordinary thermometer and is the direct

measure of sensible heat present in air.

3et &'l& Tem!erat're 6FB(7 4t is temperature indicated by thermometer whose glass bulb is co#ered by

a piece of wet cloth 4t is a measure of enthalpy of air.

H'midification 'umidification is adding moisture to air keeping its B( constant.

eh'midification ehumidification is remo#al of moisture at constant B(.

∗ ,ooling and dehumidification is usually done in summer air conditioning.

∗ 'eating and humidification is usually done in winter air conditioning.

H'man Comfort:

∗ 'uman comfort is mainly dependent on four factors namely 6i7 temperature 6ii7 humidity 6iii7 mo#ement

of air

6i#7 %urity of air.

* 'uman comfort conditions maintained by summer and winter air+conditioning system are 6)><. T 1< ,7&6>; >G7 0 ' and 6)1< T 1< ,7& >;G 0' 6-;G min7 respecti#ely.

TH,"O@/$"CS

1.; e%iew of f'ndamentals

1.1Tem!erat're 4t is defined as the degree of hotness or the le#el of heat intensity of a body. 5 hot body as

a higher temperature and cold body as the lower temperature. (emperature of a body is measured in differentscale.

,on#ersion between #arious scales of temperature

7

100 ' −32

180 8 −273

100 , temperature in ,elsius& (emperature in ahrenheit& 9

(emperature in 9el#in. . H

5t reading + 2;< both centigrade and ahrenheit gi#es same readings +

Thermometers and their ranges

∗ Mercury glass thermometer based on the expansion of mercury with increase of temperature. 4ts

approximate range is from ->< , to ->;< ,.



∗ 5lcohol in glass thermometer is used for measuring temperature range is from + C;< , to =;< ,.

∗ %entane is used in glass thermometer range is from + );;< , to -;< ,.

∗ ,onstant #olume gas thermometer is suitable for measuring temperatures in+the range from +):@< , to+

1:;;< ,

∗ !lectrical thermometers are used to measure both low and high temperatures in the range from + )=)< , to

1:;;< ,

∗ %yrometer are used for measuring hi temperatures usually mo#e >;;< ,.

∗ (hermocouple thermometer can be used for measurement of a rapidly changing temperature. 5pproximaterange is from +)>; <, to >;;<,. .

5bsolute Scale 5 scale with + )=-< , as zero and the magnitude of degree same as that of the centigrade

scale is called the absolute scale or 9el#in scale of temperature. 4t is denoted by "9".

<9 <, )=-

$&sol'te 4ero 4t is the temperature of + )=-< c at which the pressure and #olume of a perfect gas becomes

zero.&

1.) +ress're defined as force per unit area.

/nits in mks is kgfDcm) 6or7 kgDcm) %S4 %ascal EDm)& 6used for #ery small unit7& or bar&

1 bar 1;> EDm) 1;; 9EDm) 1;; 9 %a.

%ressures also stated in mm or cm of mercury

∗ Barometer is an instrument used for measuring atmospheric pressure.

∗ Manometer is an instrument used for measuring low pressure.

$tmos!heric +ress're 6%at 7 (his is the pressure exerted by air. 4ts #alue at mean sea le#el is 1.;-- 9gDcm)

6or7 1.;1- bar 6or7 barometric height of =:; mm of mercury.

$&sol'te +ress're 6%abs7 5bsolute zero of pressure will 8ccurs when molecular momentum is zero. Such asituation can occur only when there is a perfect #acuum. (he pressure measured from this le#el is called

absolute pressure.

*a'ge +ress're 6%g7 4nstruments and gauges used to measure the #alue of pressure& actually measure

difference between the fluid pressure and the pressure of fluid 6generally air7 surrounding the gauge.

% %abs + %atm

acuum %ressure 6%.7 Fhen the pressure of fluid is less than atmospheric pressure. (he gauge reads on the

negati#e side of atmospheric pressure. (his pressure is known as #acuum.

%%atm + %abs

1.- Heat heat is defined as the form of energy that is transferred by #irtue of temperature difference.

*/nits in Mks ,al 6or7 9cal& S.1 J 6or7 9.J

Calorie (he amount of heat reAuired to raise the temperature of 1 gm of water from 12-< , to 1>.><,

1 ,al 2.) J

Heat recei%ed or re7ected &( a &od( (he amount of beat recei#ed or re3ected by a working body during the

process of heating or cooling is gi#en by

Rmc 6()+(17

Fhere R heat gained or lost by the body in 9cal

m mass of the body in kg. 6()+(17 (emperature rise of body ,< or <9.



, Specific heat of substance 9calDkg< k.

1.2 S!ecific heat efined as the amount of heat reAuired to rise temperature of a unit mass of any substance

through 1<.

S!ecific heat at constant !ress're , p (he amount of heat reAuired to raise temperature of a unit mass of

any substance through 1< at constant pressure is called specific heat at constant pressure.

S!ecific heat at constant %ol'me ,# (he amount of heat reAuired to raise temperature of a unit mass of anysubstance through 1< at constant #olume is called specific at constant #olume.

,p for air ;)2 9calDkg< 9. ,# for air ;.1= 9calDkg< 9. (he ratio of ,pD,# is called adiabatic index 6r7

for air r 1.2

1.> "echanical e)'i%alent of heat (he relation between the unit of work. (his relation is denoted by J"

and is known as Joule"s eAui#alent or mechanical eAui#alent of heat. +

R FDJ& J 2)= kg kcal

#.0 Laws of !erfect gases :

).1 Bo(leEs Law (emperature being constant& pressure of a certain mass of gas is in#ersely proportional to

its #olume.

% Q1

) %1 1 %) )

).) CharleEs Law %ressure being constant& #olume of a certain mass of a gas is directly proportional to

absolute temperature.

α

(

) 1

T 1=

) 2

T 2

).- *a( L'ssac Law olume being constant pressure of a certain mass of a gas is directly proportional to

absolute temperature

% α (

P1

T 1=

P2

T 2

).2 $%agadroEs Law: /nder identical conditions of pressure and temperature eAual #olume of all gases

contain same number of molecules.

8ne kg molecules of any gas at E(% occupies )).2 m- of #olume and it contains :x1;)- molecules.

?eneral gas eAuation Both Boyle"s law and ,harles law are combined together& which gi#es a general gas

eAuation.

P1

) 1

T 1=

P2

) 2

T 2

,haracteristic eAuation of gas 4t is modified form of general gas eAuation&

% M0(

P0O is known as characteristic gas constant. gas constant for air )@.)= kg mDkg< 9 in M9S

0 ;.)C= 9JDkg <9 in S4



): /ni#ersal gas constant 6or7 molar constant 4t is the product of the gas constant and the molecular weight

of the gas.

0 u M0 Fhere 0 u is uni#ersal gas constant M is molecular weight of the gas 6kg. mole7

0 is gas constant

(he characteristic gas eAuation may be written in terms of molecular weight as % 0(

(he #alue of 0 u is same for all gases.

(he #alue of uni#ersal gas constant C2C kg ml kg. mDkg.moleD<9 in M9S

0 u C.-12 9JDkg mole< 9 in S4

).= 6o'leEs Law 4nternal energy of a gas is a function of temperature only and is independent of change in

pressure and #olume.

,hange in internal energy is proportional to change in temperature.

-.; Latent Heat (he amount of heat absorbed during a change of state without rise in temperature is called

$atent 'eat.

Latent heat of f'sion of ice (he latent heat of fusion of ice is the amount of heat reAuired to amen unit mass

of ice at ;< , into the water at ;< ,. alue of latent heat of fusion of ice 6$7

,?S System C; calDgm S. 4 System -2; x 1;- JDkg

Latent heat of Steam or; Va!o'risation of water (he latent heat of steam is the amount of heat reAuired

to con#ert unit mass of water at 1;;< , into steam at 1;;< ,.

$atent heat of steam in ,?S system >2; calDgm

S4 system ).): x 1;: JDkg

5.0 Thermod(namic S(stems:

S(stem is defined as a Auantity of matter or region under study.

Surroundings !#erything external to the system is called surroundings.

Bo'ndar( (he system is separated from the surroundings is boundary.

O!en S(stem Both mass and energy transfer take place across the system.

Closed s(stem 4s a constant mats system& across the boundary of which only energy transfer take place.solated S(stem 4s a one in which there is no interaction either of energy or mass with the surroundings.

2.1 Thermod(namic +ro!erties

ntensi%e !ro!erties (here are independent of the mass in the system.

!xamples %ressure& temperature& density etc.&

,8tensi%e !ro!erties (hese properties are related to Mass. 4f mass is increased& the #alue of the extensi#e

properties also increase.

!xamples olume& weight& enthalpy& entropy& internal energy.

>.; Laws of Thermod(namics

>.1 4eroth law of Thermod(namics Fhen two bodies are in thermal eAuilibrium separately with a third

body then they are also in thermal eAuilibrium with each other. 4t is the basis of temperature measurement.



>.) irst law of thermod(namics+ Fhen a system executes a cyclic process& the algebraic sum of work

transfer is eAual to algebraic sum of heat transfer 6or7 the heat and Mechanical work are mutually con#ertible.

>- Second law of Thermod(namics 9el#in plank statement 4t is impossible to construct an engine

working on a cyclic process& whose sole purpose is to con#ert all the heat supplied to it into eAui#alent

work.

,lausius statement 'eat does not flow from a body at lower temperature to a body a higher temperature

without any external agency.

<.5 Thermod(namic !rocesses:

∗ 'eat transferred during a constant #olume process is eAual to change in internal energy and work done is

zero.

∗ 4nternal energy and temperature of a substance is ,onstant in an 4sothermal process.

∗ 4n a adiabatic process the system will not ha#e any heat exchange with the surrounding.

∗ Fork done by the throttling or free expansion process is always zero.

,fficienc( of heat engine /=91−92

91

=1−92

91

Fhere R1 is the heat absorbed by engine from source. R) is the Auantity of heat re3ected to the Sink.

∗ or cannot engine working between temperature (1 and ( the efficiency is gi#en by

/=T

1−T

2

T 1=1−

T 2

T 1

:.; 'els and Com&'stion:

:.1 'el 5 fuel may be defined as substance 6containing mostly carbon and hydrogen7 which on burning

with oxygen in the atmospheric air& produces a large amount of heat. + +

∗ Food& peat& lignite& bituminous and anthracite coals are natural& solid fuels& coke& charcoal and

pul#erized coal are artificial solid fuels.

∗ ,rude 8il is a natural liAuid fuel& here gasoline& kerosene& paraffin and hea#y oils are artificial liAuid

fuels.

∗ Eatural gas is a natural gaseous fuel& coal gas& producer gas and mond gases are artificial gaseous fuel

:.) Higher 6or7 *ross Calorific %al'e: 'eat liberated by unit mass or unit #olume of fuel when burned

completely and products are cooled down to atmospheric temperature is called higher calorific #alue.

∗ 'igher calorific #alue of wild or liAuid fuel can be determined by Bomb ,alorimeter. (he

,ombustion of fuel takes place at constant #olume in it.

∗ JunkerOs gas calorimeter is used to determine higher calorific #alue of gaseous fuel.

:.- Lower Calorific Val'e Fhen the heat absorbed or carried away by the products of combustion is not

reco#ered and steam formed during combustion is not considered& then the amount of heat obtained per kg of

the fuel is known as lower or net calorific #alue.

:.2 Com&'stion of f'els

∗ 8ne kg of carbon reAuires CD- kg of 8xygen for complete combustion and produces 11D- kg of carbon

dioxide.



∗ 8ne kg of ,arbon reAuires 2D- kg of 8xygen and to produces =D- kg of carbon monoxide.

∗ 8ne kg of hydrogen reAuires C kg& of 8xygen and produces @ kg of water or steam.

∗ 1 kg of methane reAuires 2 kg of 8xygen and produces 1D2 kg of carbon dioxide and @D2 kg of water 6or7

steam.

∗ 1 m- of ,arbon reAuires 1 m- of 8xygen and produces 1 m- of carbon dioxide.

∗ (he olumetric analysis of dry fuel gases may experimentally be obtained by 8rsat apparatus.

∗ 5tmospheric air consists of )-G 8xygen and ==G Eitrogen& by weight and )1G 8xygen and =@G

nitrogen by #olume.∗ %etrol is distilled at temperature +:>< to ));< , and 9erosene is distilled at ));< c to -2> < ,

Bituminous coal has the highest calorific #alue.

Transmission of heat

Heat 'eat is defined as the form of energy that is transferred by #irtue of temperature difference. 'eat

always flow from a body at higher temperature to a body at lower temperature. (his transmission of heat

follows three methods.

(hey are

Cond'ction (he transmission of heat in a body without mo#ement of its particles. !.g. 4n solids

Con%ection (he transmission of heat from one part to another in a body by the actual mo#ement of its

particles is called con#ection. !.g. 4n liAuids and gases heat flow by the method.

adiation (he transmission of heat from one place to another without any material or medium in between is

called radiation.

!.g. !arth recei#es heat from the Sun.

D.# Thermal Cond'cti%it(+(he amount of heat R" transmitted by conduction in a body is

R

82 (T 1−T

2 ) t

L

Fhere "5" is the cross sectional area& (T 1−T

2 ) is the temperature difference between the two faces.

"$O is the length of the rod. PtO time of flow of heal &"9" is the coefficient of thermal conducti#ity 6or7 (hermal

conducti#ity of the material.

/nits V ,.?.S ,alDs.cmD<9 S.4 JDsmD< k 6or7 wDm< 9

=.- $&sor!tion of Heat Fhen radiant heat is incident on the surface of a body& a part of it is absorbed and

the remaining part is reflected. (he process in which heat is absorbed by a body is called absorption of heat.

=.2 $&sor!ti%e +ower (he absorpti#e power of a surface is the ratio of the amount of heat absorbed by a

surface to the amount of heat incident on it.

=.> eflecting +ower 4t is the ratio 8f the amount of heat reflected by a surface to the amount of the heat

incident on it.

=.: ,missi%e +ower (he emissi#e power of a surface is the amount of heat radiation emitted per second per

uniarea of the Surface per 1< , excess of temperature o#er the surroundings.

=.?Transmitting +ower 4t is the ratio of the amount of radiation passing through it to the total amount of

radiation incident on it.



=.C Black Bod( 5 perfect black body is one which absorbs all radiations incident on it. 5 perfect black body

is a good absorber as well as emitter of heat.

∗ %latinum black absorbs @CG and lamp black about @:G of the incident radiation.

=.@ Stefan Bolt9mann Law: (he rate of loss of heat energy by radiation per unit area of the surface of a

perfectly black body is directly proportional to the fourth power of its absolute temperature.

! : 5(2 is called Stefan"s constant a >.:=> x 1;+C FDm)<9 2

=.1; =irchorffGs law of radiation (he ratio of the emissi#e power to the absorpti#e power of all bodies is

the same and is eAual to the emissi#e power of a perfectly black body.

=.11 3ienEs is!lacement Law: (he radiation energy consists of different wa#elengths. 5ccording to this&

the maximum wa#elength energy is in#ersely proportional to the absolute temperature of the radiation.

m ( ,onstant

=.1) /ewtonEs law of Cooling: (he rate of cooling of a body is directly proportional to the mean excess of

its temperature o#er the surrounding.

C.; =inetic Theor( of gases

∗ (he pressure exerted by as gas is gi#en by % 1

3 mnc+)

Fhere "n" is the number of molecules of the gas per unit #olume.

PmO is the mass of each molecule.

Pc+)O is the mean sAuare #elocity of the gas molecules.

@.; +ro!erties of Steam Steam is #apour of water& and is in#isible when pure and dry. 4t is approximatelyacts like a gas.

∗ Steam does not obey laws of perfect gases& until it is perfectly dry.

∗ Sensi&le heat 'eat reAuired to raise temperature of one kg of water& when heated at a constant

pressure from ;< , to the temperature of formation of steam. "

'eat absorbed 6or7 sensible heat 6h7 tsat 9cal

Latent heat of steam or; Latent heat of Va!o'risation 4t is the amount of heat reAuired to e#aporate 1 kg

of water at its boiling point without change of temperature. 4t is denoted by P$O.

(otal heat of steam h x$ for wet steam K h $ for dry steam

where "x" is the dryness fraction.

S'!er heated Steam: Fhen the dry steam is further heated at a constant pressure& thus raising its

temperature& it is said to be superheated steam.

* (he total heat reAuired for the steam to be superheated is total heat of dry steam and heat of super heat.

'sup h $ , p 6(sup U (sat7

(he difference 6(sup U (sat7 is known as degree of Superheat.

r(ness fraction or )'alit( of wet steam 4t is the ratio of the weight of actual dry steam& to the weight of

same Auantity of wet steam& and is generally denoted by "x".



_

W s

W s+W

Fhere Fs 5ctual weight of dry steam. F Feight of water in steam.

Tri!le +oint 4t is the point where three states of matter& i.e.& Solid& liAuid and #apour coexist in eAuilibrium.

(he triple point of water is )=-.1:< 9 at pressure of :1;.) %ascalOs.

Critical +oint Fhen the pressure and saturation temperature increases& the latent heat of steam is decreases.

4t becomes zero at a point& where liAuid and dry steam lines meet is known as the critical point. (he

temperature corresponding to critical point is known as critical temperature and the pressure is known as

critical pressure.

∗ or water& the critical temperature is -=2< , and critical pressure is ))> kgDcm ) 6or7 )).1 bar.

1;.; Steam Boilers

1;.1 5 steam generator or boiler is& usually& a. closed #essel made of steel. 4ts function is to transfer the heat

produced by the combustion of fuel to water& and ultimately to generate steam.

* Boilers are mainly classified as fire tube and water tube boilers.

∗ 4n fire tube or smoke tube boilers& the flames and hot gases& produced by combustion of fuel& pass

through the tubes which are surrounded by water.

∗ !xamples of fire tube boiler are simple #ertical boiler& ,ochran boiler& $ancashire boiler& ,ornish boiler&

scotch marine boiler and locomoti#e boiler.

∗ 4n water tube steam boilers& the water is contained inside the tubes which are surrounded by flames and

hot gases from outside..

∗ !xamples of water tube boilers are Babcock and Filcox boiler& Sterling boiler& $amont boiler& Benson

boiler and $offler boiler.

∗ ,ornish boiler has one large flue tube and $ancashire boiler has two large diameter flue tubes.

$ocomoti#e boiler is a multi tubular horizontal internally fired and mobile boiler. (here are about 1>= thin

fire tubes and )2 thick or superheated tubes. (he draught is produced by the exhaust steam from engine

which is discharged through the blast pipe to the stack or chimney.

10.# Boiler "o'ntings Boilers are pro#ided with certain mountings which are essential for their safe

operation.

6a7 3ater le%el indicators: 4t is the important fitting& which indicates the water le#el inside the boiler to

an obser#er.

6b7 +ress're ga'ge: 5 pressure gauge is used to measure the pressure of the steam inside the boiler. (he pressure gauge is generally used is of Bourdon tube.

6c7 Safet( Val%es (his is a de#ice attached to the steam chest for pre#enting explosions due to excessi#e

internal pressure of steam. (he function of a safety #al#e is to blow off the steam when the pressure of steam

inside the boiler exceeds the working pressure.

The( are fo'r t(!es 6i7 $e#el safety #al#e 6ii7 ead weight safety #al#e 6iii7 high steam and flow water

salty #al#e 6i#7 Spring loaded salty #al#e.

∗ Spring loaded salty #al#es are mainly used for $ocomoti#e and marine boilers.

6d7 Steam Sto! Val%e 4t is the largest #al#e on the steam boiler. (he main functions of a stop #al#e are

to control the flow of steam from the boiler to the main steam pipe and to shut off the steam completely whenreAuired.

6e7 Blow off cock 4t is fitted to the bottom of a boiler drum& (he principal functions of a blow off cock are to

empty the boiler whene#er reAuired and to discharge the Mud& scale or sediments which are accumulated at

the bottom of the boiler.



∗ ighter bombers use turbo 3et type of engine.

∗ 5ir fuel ratio in a Jet engine will be of the order of :;1

esign of "achine ,lements

1.; Screw threads 5 screw thread is formed by cutting a continuous helical groo#e a cylindrical surface.

(he helical groo#es may be cut either right hand or left hand.

∗ (he threaded portion engages with a corresponding threaded hole in the nut or machine part.

∗ Screws ha#e two general purposes in engineering. (hey acts as fastening to secure one member to

other member by to transmit power.

Terms 'sed in Screw threads

"a7or diameter 4t is the largest diameter of an external or internal screw thread. (he screw is specified by

this diameter. 4t is also known as outside or nominal diameter.

"inor diameter 4t is the smallest diameter of an external or internal screw thread. 4t is also known as core

or root diameter.

+itch diameter 4t is also called effecti#e diameter. 4t is the diameter at one half of the thread depth.

+itch 4t is the distance between the two ad3acent threads measured parallel to the axis of the screw.

Lead (he distance a screw thread ad#ances axially in one turn.

$ead pitch x no. of starts.

Crest 4t is the top surface 3oining the two sides of a thread.

oot 4t is the bottom surface of the thread.

e!th of thread 4t is the distance between the crest and root of the thread measured normal to the axis.

Heli8 angle (he angle made by the helix of the thread at the pitch diameter with a plane perpendicular to the

axis.

Thread angle 4t is the angle between two flanks measured on axial plane.

%itch

Spiral angle Spiral angle Pitc +

Pitc + Diameter

1.# orms of Screw threads (he following are the #arious forms of screw threads.

British standard with worth B.S.3; thread (hese are rounded threads. (he angle of thread is >><

.British standard pipe 6B.S.%7 threads with fine pitches are used for steel and iron pipes and tube carrying

fluids.

British $ssociation B.$; thread (hese are rounded threads. 5ngle of thread is 2= <. (hese threads are

often used on screw for precision work.

$merican /ational Standard threads SS threads; (hese threads ha#e shape and included angle of

thread of :;< . (he tops and bottoms of threads are flat.

nified Threads (he thread form shaped and angle being :;<. (he thread has rounded crests and roots.



S)'are threads (hese threads are named so because of their shape. (he depth and width of the thread is

eAual to half the pitch. (hese are widely used for transmission of power in either direction. Because of higher

efficiency Such type of threads are usually found on the feed mechanisms of machine tools& #al#e spindle&

screw 3ack etc

$cme threads 4t is a modification of sAuare threads 4t is much stronger than sAuare read and included angle

is )@<.(hese threads are freAuently used on screw cutting lathe& bench #ice etc

=n'ckle threads: (hese are sAuare thread with corners rounded off& which make the threads capable of

withstanding great strain rough use. epth of thread 1

2 pitch& radius at top and bottom 1

4 x

pitch.

B'ttress threads (he thread angle is 2><.(he front face is perpendicular to the axis of the screw. 4t used for

transmission of power in one direction only. (he railway carriage couplings ha#e buttress threads.

"etric thread 4t is an 4ndian Standard thread and is similar to BSF threads. 4t has an included angle of :;<.

1.2 T(!es of screw fastenings Screw fasteners are used to fasten or hold parts together. (hese are allowed

the parts to be disassembled whene#er necessary.

Thro'gh &olts 5 through bolt is a cylindrical bar with threads for the nut at one end and head at the other

end. 4t is passed through drilled holes in the two parts to be fast end together and clamps them securely to

each other as the nut is screwed on to the threaded end.

Ta! &olts 5 tap bolt or screw differs from a bolt 4t is screwed into a taped hole of one the parts to be

fastened without the nut.

St'ds Stud is a round bar threaded at both ends. 8ne end of the stud is screwed into a tapped hole of the

parts to be fastened& while the other end recei#es a nut on it.

Ca! Screws (he cap screws are similar to tap bolts except that they are of small size and a #ariety of shapes

of heads.

"achine Screws (hese are similar to cap screws with the head slotted for a screw dri#er. (hese are

generally used with a nut.

Set Screws (hese are used to pre#ent relati#e motion between the two parts. (hey may be used instead of

key to pre#ent relati#e motion between a hub and a shaft in light power transmission members.

1.5 Locking e%ices:

6am n't or lock n't 5 most common locking de#ice is a Jam $ock or check nut. 5 thin lock nut is first

tightened down with ordinary force& and then the upper nut tightened down upon it.

Castle n't 4t consists of a hexagonal portion with a cylindrical upper part which is slotted in line with the

centre of each face& the split pin passes through two slot in nut and a hole in the bolt. ,astle nuts are

extensi#ely used in automobile industry.

S!ring lock washer (hese are made from spring steel and may be split single or multi coil. (he split type

washer has the edges of the split raised in opposite directions.

1.< esignation of Screw Threads

Si9e designation of screw threads 5ccording to the 4ndian standards& the size the screw thread is

designed by the letter "M" followed by the diameter and pitch& the two being separated by the sign "_".

Tolerance designation (his shall include



6a75 figure designating tolerance grade = for fine grade& C for medium grade and @ for coarse grade.

6b75 letter designating the tolerance position as& ' for unit thread&OdO for bolt thread with allowance and "hO

for bolt thread without allowance.

!.gM1 ;+ Cd means& 5 bolt thread of l; mm size of coarse pitch and with allowance on the threads and

normal tolerance grade

1.> Tee headed &olt 4t is used to damn work pieces on a machine tool table.1.D ,(e &olt: 4t is used to lift hea#y machines& like electrical motors.

1.? 3ing n't 4t is used where ad3ustment reAuired to be made freAuently. 4t can be open by a thumb and

finger. !.g. hack saw rebate connected to frame by a wing nut.

1.A 3asher 4t is a cylindrical piece of metal placed low the nut to pro#ide flat surfaces. 4t allows the nut

to be screwed or more tightly 5 washer is specified by its hole diameter.

#.0 =e(s and Co'!lings:

• 5 key is a piece of metal inserted between the shaft and hub of the pulley to connect these together in

order to pre#ent relati#e motion between them.

∗ 9eys are di#ided into fi#e types& namely&

6i7 Saddle keys 6ii7 Sunk keys 6iii7 (angent keys 6i#7 round keys and 6#7 Splines

i. Saddle ke(s (hese are pro#ided fully in the hub only. (hese keys are used for light loads as there is a

tendency to slip under hea#y loads.

ii. S'nk =e(s (hese are pro#ided half in the keyway of the shaft and half in the key way of the hub or

boss of the pulley. (he sunk keys are of following types& 0ectangular sunk key& sAuare sunk key&

parallel sunk key& gib head key& father key and woodruff key.

3ood r'ff ke( is an easily ad3ustable key. 4t is a piece from a cylindrical disc ha#ing segmental cross

sections.(his key is largely used in machine tools and automobile construction.

*i& head ke( 4t is a rectangular sunk key with a head at one end known as gib head. 4t is usually pro#ided to

facilitate the remo#al of key&

(he usual proportions of the gib head key are width& w d

4 and thickness at large end t d

6 & width F

d

4 and thickness of key 6t7 2$

3∨

d

6

FhereOdO is the diameter of the shaft or diameter of hole in the hub.

ectang'lar S'nk =e(: 4t has rectangular cross section and ha#ing uniform taper on the top side is in 1;;.

S)'are S'nk =e( 4t has sAuare cross section and tapered 1 in 1;; on the top side. (he width and thickness

are eAual to i.e. Ftd

4

eather =e( 5 key attached to one member of a pair and which permits relati#e axial mo#ement is known

as feather key.

Tangent =e(s (hese keys are fitted in pair at right angles and each key is to withstand torsion in one

direction only. (hese are used in large hea#y duty shafts.

o'nd =e(s (he round keys are circular in section and fit into holes drilled partly in the shaft and partly in

the hub. (hese are usually considered to be most appropriate for low power dri#es.



S!lines Some times& keys are made integral with the shaft which fits in the keyways broached in the hub.

Such shafts are known as splined shafts.

Shaft Co'!lings: $ coupling is a de#ice used to make permanent or semi permanent connection between

two ad3oining shafts.

∗ Shaft couplings are used to pro#ide for the connection of shafts of units that are manufactured

separately such as motor and generator& and to pro#ide for misalignment of the shafts.

∗ ,ouplings are di#ided into+ two groups& 6i7 rigid coupling 6ii7 lexible coupling.2.1 igid co'!ling 0igid coupling is a solid couplingK it is used to connect two shafts which are perfectly

aligned.

∗ Slee#e or muff coupling& clamp or split muff or compression coupling& and flange couplings are rigid

type of couplings.

2.# le8i&le co'!ling 4t is used to connect two shafts ha#ing both lateral and angular misalignment.

∗ Bushed pin type coupling& uni#ersal coupling and 8ldham couplings are flexible type of couplings.

∗ 5 uni#ersal or hookOs coupling is used to connect two shafts whose axis intersects at a small angle. (he

inclination of the shafts may be constant& but in actual practice& it #aries when the motion is transmitted fromone shaft to another. 'ooke"s couplings are mainly found in the transmission from the gear box to the

differential or back axle of the automobiles.

5.0 Shafts 5 shaft is rotating machine element which is used to transmit power from one place to at another.

∗ Shafts are usually cylindrical& but may be sAuare or cross shaped in section. (hey are solid or hollow

in cross section.

∗ 5s axle is similar in shape to the shaft& it is a stationary machine element and is used for the

transmission of bending moment only

∗ Spindle is a short shaft that imparts motion either to a cutting tool or to a work piece.

∗ (he material used for ordinary shafts is mild steel. Fhen high strength is reAuired on alloy steel such

as nickel& nickel chromium steel is used.

∗ 5 shaft may be a transmission shaft& such as counter shafts& line shafts& head shafts and all factory

shafts 6or7 a machine shaft such as crank shaft.

∗ $ength of standard shaft will not exceed = meters on the account of transport difficulties.

∗ (he twisting moment or torAue transmitted by the shaft

6i7 ( π

16

f s d- where ( (wisting moment 6or7 (orAue &f s (orsional shear stress& d

diameter of the solid shaftH

6ii7 or a hollow shaft ( π

16

f s d-61+k 27 Fhere 9 ratio of inside diameter and outside diameter of the shaft

di Ddo.

di and do outside and inside diameter of the hollow shaft.

6iii7 %ower transmitted in watts by the shafts p %2 πNT

60 watt K Fhere ( (wisting moment in E+m

E speed of the shaft in r.p.m

6i#7 'orse power transmitted by the shaft& %2 πNT

4500 hpK Fhere ( (wisting moment in kg.f.m

E Speed of the shaft in r.p.m.



>.0 i%eted 6oints

∗ 5 ri#et is a short cylindrical bar with a head integral to it. (he cylindrical portion of the ri#et is called

shank or body and lower portion of shank is known as tail.

∗ (he ri#ets are used to make permanent fastening between the plates such as in Structural work& ship

building& bridges& tanks and boiler shells.

∗ (he material of the ri#ets must be tough and ductile. (hey are usually made of low carbon steel&

nickel steel& brass& aluminium and copper.

<.1 T(!es of ri%et heads

∗ (he snap heads are usually employed for structural work& machine ri#ets and boiler plates.

∗ (he counter sunk heads are mainly used for ship building where flat surfaces are necessary.

<.# T(!es of i%eted 6oints:

∗ La! 7oint 5 lap 3oint is that in which one plate o#erlaps the other and the two plates are then ri#eted

together.

∗ B'tt 7oint 5 butt 3oint is that in which the main plates are kept in alignment butting and a co#er plate is placed either on one side or on both sides of the main plates.

<.2 Terms 'sed in i%eted 6oints:

* +itch 4t is the distance from the centre of one ri#et to the centre of the next ri#et measured parallel to the

seam.

* Back +itch 6% b 7 4t is the perpendicular distance between the centre lines of the successi#e rows.

* iagonal +itch 6%d 7 4t is the distance between the centreOs of the ri#ets in ad3acent rows of zig+zag

ri#eted 3oint.

∗ "argin or "arginal !itch 6m7 4t is the distance between the centres of ri#et hole to the nearest edge of the

plate.

<.5 ail'res of a i%eted 6oint

∗ Tearing of the !late at an edge 5 3oint may fail due to tearing of the plate at an edge. (his can be

a#oided by keeping the margin& m 1.> d& whereOdO is the diameter of the ri#et hole.

∗ Tearing of the !late across a row of ri%ets (he resistance offered by the plate against tearing is

known as tearing resistance or tearing strength. (earing resistance& %t 6%+d7 t x f t

∗Shearing of the ri%ets (he resistance offered by a ri#et to be sheared off is known as shearingresistance.

Shearing resistance 6%s7 nπ

4 d) f s 6for single co#er7 1.C=> x nπ

4 d) f s 6for double co#er7

∗Cr'shing of the ri%ets (he resistance offered by a ri#et to be crushed is known as crushing resistance.

,rushing resistance& %c n.d.t. f c

<.< iameter of ri%ets (he diameter of a ri#et hole 6d7 may be determined by using /nwin"s empirical

formula& i.e.& d : √ t 6Fhere t is greater than C mm7&

>.0 Cotter 7oints



∗ 5 cotter is a flat wedge shaped piece of rectangular cross. Section and its width is tapered either on

one or both sides.

∗ (he taper #aries from 1 in 2C to 1 in )2.

∗ 5 cotter 3oisnt is a temporary fastening and is used to connect rigidly two co+axial rods&

∗ 4t is usually used in connecting a *ton to the cross head of a reciprocating steam engine.

D.0 l( 3heel

∗ 5 fly wheel used in machines ser#es as a reser#oir which stores energy during the period when the

supply of energy is more than the reAuirement and releases it during the period when the reAuirement

of energy is more than supply.

∗ ly wheel is a main part in 4., engines& reciprocating compressors and pumps.

Co-efficient of fl'ct'ation of s!eed (he difference between maximum and minimum speed during a

cycle is called the maximum fluctuation of speed. (he ratio of maximum fluctuation of speed to mean

speed is called coefficient of fluctuation of speed.

,oefficient of fluctuation of speed& ,s 2( N 1− N 2)

N 1+ N

2

E1 and E) is maximum and minimum speed in rpm during a cycle respecti#ely.

Technical Part 1

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Transcript of Technical Part 1