FABRICATION OF

SPUR GEAR

Department of Mechanical Engineering

Khulna University of Engineering & Technology

Khulna-9203, Bangladesh

Supervised by

Md.Golam Kader

Professor,

Md Rasedul Islam

Lecturer,

Department of Mechanical

Engineering, KUET

Submitted By

Md Rezowan Kabir [1205016]

Md Hasanuzzaman [1205017]

Md Abul Kashem Hemel [1205018]

Md Ashik Mahmud [1205019]

Saikat Biswas [1205020]

Course ME 3118

TABLE OF CONTENTS

Page

Acknowledgement ------------------------------------------------ i

Abstract -------------------------------------------------------------- ii

List of figures ------------------------------------------------------- iii

List of tables -------------------------------------------------------- iv

Nomenclatures ------------------------------------------------------ v

Chapter 1: Introduction

1.1 Objectives--------------------------------------------------- 01

1.2 Introduction-------------------------------------------------- 02

1.3 Types of Gear ------------------------------------------------03

1.4 Spur Gear-----------------------------------------------------04

1.5 Application ----------------------------------------------------05

Chapter 2: Gear Terminology

2.1 Gear Terminology------------------------------------------06

2.2 problem-------------------------------------------------------09

2.3 Solution -------------------------------------------------------10

2.3 solidworks design--------------------------------------------13

2.4 Keyshot Rendering -----------------------------------------14

Chapter 3: Construction

page

3.1 Materials-------------------------------------------------- 15

3.2 why we choose Cast iron -------------------------------16

3.3 Manufacturing process of spur gear ------------------ 16

3.4 Reason for choosing Milling process-------------------17

3.5 Milling Process--------------------------------------------17

3.6 Methodology ----------------------------------------------18

Chapter 4: Conclusion

4.1 Result & Discussion --------------------------------------20

4.2 Final project ------------------------------------------------20

4.3 Conclusion --------------------------------------------------21

Chapter 5: References

5.1 References --------------------------------------------------22

ACKNOWLEDGEMENT

Thanks to almighty God for enabling and helping the authors to carry out

this project work.

The authors would like express sincere gratitude to their supervisors

Md.Golam Kader, Professor and Md. Rasedul Islam, Lecturer,

Department of Mechanical Engineering, KUET, for their consultation and

discussion which were essential to carry out this work. They were always

accessible and willing to help them to carry out this project.

Authors want to express their sincere gratitude to Prof. Dr. Nawsher Ali

Moral, Head, Department of Mechanical Engineering, KUET, who gave

them permission to work in machine shop, welding shop and heat engine

laboratory.

Also thanks to all the lab assistants who helped the authors in order to

achieve the project goal.

“Authors”

i

ABSTRACT

A gear is a rotating machine part having cut teeth, which mesh with

another toothed part to transmit torque, in most cases with teeth on the

one gear being of identical shape, and often also with that shape on the

other gear. Gear is used for Changing the direction through which power

is transmitted (i.e. parallel, right angles, rotating, linear etc.), Changing

the amount of force or torque, Changing RPM.

Spur Gear is a very important type of gear. Spur gears are the most

commonly used gear type. They are characterized by teeth which are

perpendicular to the face of the gear. Teeth are parallel to axis of rotation.

In this project work a spur gear was made based on a mathematical

problem from “problem book of FAIRES VIRGIL MORING, “DESIGN

OF MACHINE ELEMENTS”, 4th edition, The Macmillan Company, New

York/Collier-Macmillan Limited, London”. The gear was made by cast

iron. Because of its strength & availability.

In this project work, finally a spur gear was completed and every updates

were given regularly.

ii

List of Figures

Figure Title page

Figure 1.1 Gears 2

Figure 1.2 Gear meshing 3

Figure 1.3 Spur gear 4

Figure 2.1 Spur gear terminology-1 6

Figure 2.2 Spur gear terminology-2 7

Figure 2.3 Pressure angle of Spur gear 8

Figure 2.4 Dimensions of Spur gear 13

Figure 2.5 Rendering images 14

Figure 3.1 Milling process 18

Figure 3.2 Milling machine 19

Figure4.1 Manufactured Spur Gear 20

iii

List of tables

Table Title page

Table 2.1 calculation for pitch diameter 11

iv

Nomenclature

Symbol Description

PD------------------------------------------- Diametral pitch

Hp------------------------------------------- Horse power

kf -------------------------------------strength reduction factor

Ft----------------------------------------- Transmitted load

FD--------------------------------------- Dynamic load

Fs------------------------------------------ Safe load

mw ------------------------------------ Velocity ratio

vm ------------------------------------ pitch line speed

b---------------------------------------- Face width

Np------------------------------------------------ Pinion teeth

Ng------------------------------------------------ Gear teeth

Nsf ---------------------------------------------- Service factor

v

Chapter 1

Objectives

Introduction

Types of Gear

1.1 Objectives

To Study about gear.

To Study about the classification of gear.

To Study about spur gear.

Fabrication of spur gear.

To Study of advantages and disadvantages of

spur gear.

Page 1

1.2 Introduction:

A gear is a rotating machine part having cut teeth, which mesh with

another toothed part to transmit torque, in most cases with teeth on the

one gear being of identical shape, and often also with that shape on the

other gear.

Two or more gears working in a sequence are called a gear train or, in

many cases, a transmission; such Gear arrangements can produce a

mechanical advantage through a gear ratio and thus may be considered a

simple machine.

Figure 1.1 Gears

Page 2

Gears are used to Control Power Transmission in These Ways

1. Changing the direction through which power is transmitted (i.e.

parallel, right angles, rotating, linear etc.)

2. Changing the amount of force or torque

3. Changing RPM

When two gears mesh, and one gear is bigger than the other (even though

the size of the teeth must match), a mechanical advantage is produced,

with the rotational speeds and the torques of the two gears differing in an

inverse relationship.

1.3 Types of Gear:

According to the position of axes of the shafts.

Parallel

1.Spur Gear

2.Helical Gear

Page 3

Figure 1.2 Gear meshing

3. Rack and Pinion

Intersecting

1. Bevel Gear

Non-intersecting and Non-parallel

1.worm and worm gears

1.4 Spur Gear:

Spur gears are the most commonly used gear type. They are characterized

by teeth which are perpendicular to the face of the gear. Spur gears are by

far the most commonly available, and are generally the least expensive.

Teeth is parallel to axis of rotation

Transmit power from one shaft to another parallel shaft

least expensive

Page 4

Figure 1.3 Spur gear

1.5 Applications of Spur Gear:

Metal cutting machines

Power plants

Marine engines

Mechanical clocks and watches

Fuel pumps

Washing Machines

Gear motors and gear pumps

Rack and pinion mechanisms

Material handling equipments

Automobile gear boxes

Steel mills

Rolling mills

Page 5

Chapter 2

Gear Terminology

Problem

Solution

Dimensions

Solidworks Design and keyshot

Rendering

2.1 Gear Terminology :

Pitch surface : The surface of the imaginary rolling cylinder (cone,

etc.) that the toothed gear may be considered to replace.

Pitch circle: A right section of the pitch surface.

Root (or dedendum) circle: The circle bounding the spaces between

the teeth, in a right section of the gear.

Addendum: The radial distance between the pitch circle and the

addendum circle.

Dedendum: The radial distance between the pitch circle and the root

circle.

Figure 2.1 Spur Gear Terminology [1]

Page 6

Clearance: The difference between the dedendum of one gear and the

addendum of the mating gear.

Face of a tooth: That part of the tooth surface lying outside the pitch

surface.

Flank of a tooth: The part of the tooth surface lying inside the pitch

surface.

Circular thickness (tooth thickness) : The thickness of the tooth

measured on the pitch circle. It is the length of an arc and not the length

of a straight line.

Tooth space: The distance between adjacent teeth measured on the

pitch circle.

Figure 2.2 Spur Gear Terminology [2]

Page 7

Backlash: The difference between the circle thickness of one gear and

the tooth space of the mating gear.

Module m : Pitch diameter divided by number of teeth. The pitch

diameter is usually specified in inches or millimeters; in the former case

the module is the inverse of diametral pitch.

Fillet : The small radius that connects the profile of a tooth to the root

circle.

Pinion: The smaller of any pair of mating gears. The larger of the pair is

called simply the gear.

Velocity ratio: The ratio of the number of revolutions of the driving (or

input) gear to the number of revolutions of the driven (or output) gear, in

a unit of time.

Pressure angle: Pressure angle in relation to gear teeth, also known as

the angle of obliquity, is the angle between the tooth face and the gear

wheel tangent. It is more precisely the angle at a pitch point between the

line of pressure (which is normal to the tooth surface) and the plane

tangent to the pitch surface.

Figure 2.3 Pressure Angle of spur gear

Page 8

2.2 Problem :

It is desired to transmit 30 hp at 1800 rpm of the pinion; intermittent

service; with light shock (§13.18); preferably not less than 20, 20o -full-

depth teeth on the pinion; strength reduction factor Kf = 1.25 should be

conservative; mw =1.5 Decisions must be made concerning the material

and quality of cutting the teeth. Since the design is for strength only, it

will be convenient to express Ft , Fd , vm ,face width b in terms of pitch Pd

and arrange an equation containing s and Pd convenient for iteration.

Weak material results in a relatively large pinion with high peripheral

speed. A very strong material may be unnecessarily expensive. On a

production bases carefully cut teeth should have a reasonable cost.

Specify material, accuracy of cutting, pitch, face width, and tooth

numbers.

Page 9

2.3 Solution:

Dp=Np

Pd =

20

Pd

Vm=𝜋Dpnp

12=

𝜋(20

Pd )

12*1800=

9424.78

Pd

Ft=33000ℎ𝑝

Vm

= 105.04Pd

120hp>20hp

use Buckingham’s equation

Fd= Ft+.05Vm (cb+Ft)

.05Vm+√(cb+Ft)

Assume a material of steel, as rolled AISI 1050,

Su= 102 ksi

For carefully cut teeth, Fig. AF 20, e .0001 in (min.)

Table AT 25, steel on steel, 200 F.D.

C 1660

assume

b=8.5

Pd

Page 10

Fd= 105.04Pd+.05(

9424.78

Pd)[1660(

8.5

Pd+105.04Pd)]

.05(9424.78

Pd)+√[(1660

8.5

Pd+105.04Pd)]

Fs=𝑠𝑏𝑦

PdKf

Weak pinion Table AT 24,Np =20

, Y =.0522 (Load near middle, 200 F.D.)

S=0.5Su= 0.5*102=51ksi=51000 psi

Fs=(51000)(

8.5

Pd)∗0.522)

1.25Pd

=2262

Pd

Fs= Fd Nsf

(§13.18), light shock, Nsf 1.25

Table 2.1

Pd

Fd Fs

Nsf(≤ 1.25)

7 2281.57 3694.48 1.62

8 2235.645 2828.5875 1.2652

Pd =8

b=8.5

Pd

Page 11

Np= 20 , Ng

Np = mw

Ng=20*1.2=24

b=1.0625

Np=20

Ng=24

So the pitch diameter of the gear Pd = 8

Face width b =1.0625 inch

Number of teeth = 24

Page 12

2.4 Drawing & Dimensions

Page 13

Figure 2.4 Drawing & dimensions

2.5 Rendering Image

Figure 2.5: Rendering images

Page 14

Chapter 3

Materials

Why we choose cast iron

Manufacturing process

Procedure

Final project

3.1 Materials:

1. Steel

2. Cast Iron

3. Stainless Steel

4. Aluminum

5. Bronze

6. Nylon

7. Non-metallic phenolic

Page 15

3.2Why we choose Cast Iron?

• High tensile strength to prevent failure against

static loads.

• High endurance strength to withstand dynamic

loads.

• Low coefficient of friction.

• Good manufacturability.

• Low cost

• High availability

3.3 MANUFACTURING PROCESS OF SPUR GEAR:

1. Casting

2. Milling

3. Broaching

4. Gear hobbing

5. Gear forming

Page 16

3.4 Reason for choosing Milling process:

1. It is Compatible with All Materials

2. Flexible Use

3. Short Lead Times

4. Better accuracy

3.5 Milling process:

This is one of the initial and best known and metal removal

process for making gears. This method requires the usage of a

milling machine. It is also to be noted that this method can

produce nearly all types of gears. The method involves the use of

a form cutter, which is passed through the gear blank to create the

tooth gap. This method is right now used only for the manufacture

of gears requiring very less dimensional accuracy. To put it

correctly this method is currently outdated.

Page 17

3.6 Methodology:

The gear blank is mounted on a mandrel which is supported between the

center of the dividing head and one more center at the other end, as shown

in fig. At a time one tooth space is cut by the milling cutter, and a dividing

head is used to index the job to the next required tooth space. The cutter

is chosen according to the module (or DP) and number of teeth of the gear

to the cut. This cutter is mounted on the milling arbor. Before the gear can

be cut, it is necessary to have the cutter centered accurately relative to the

gear holding mandrel. One way is to adjust the machine table vertically

and horizontally until one corner of the cutter just touches the mandrel on

one side. Both the dials (of the table and the knee) are then set to zero.

The table is then adjusted for the cutter to just touch on the other side of

the mandrel with vertical dial showing zero. The reading of the horizontal

Figure 3.1 Milling Process

Page 18

feed screw is read. This reading divided by two gives the central position

of the mandrel relative to the cutter. When the table is set centrally in this

manner it should be locked in that position. The table is then fed vertically

so that the blank just touches the cutter. The vertical dial is then set to

zero. This is required to give the depth of cut on the job.

With these settings the machine can be started and traversed along the axis

of the job to cut the tooth over the whole width of the gear. Depth is

increased slowly until it reaches the full depth of the tooth. With the depth

setting the backlash of the gear can be controlled suitably. After one tooth

space is cut, the blank is indexed through 1/z revolution by means of the

dividing head, and the process is repeated until all the teeth are cut.

Figure 3.2 Milling Machine

Page 19

Chapter 4

Result and Discussion

Conclusion

4.0 CONCLUSION:

4.1 Result & Discussion:

By analyzing the selected problem, all steps are completed to manufacture

a spur gear. All dimensions are taken based on the problem. After

completing several machining process expected spur gear is found. For

light shock the value of Nsf should be 1.25< Nsf <1.5. The value of Nsf of

the designed gear is within the range .So the design will be safe from the

failure

4.2 Final Project

Fig4.1: Manufactured Spur Gear

Page 20

4.2 Conclusion:

By performing this project we had learnt the design of spur gear, analysis

of a spur gear terminology, solving related problem, calculating safety

factor of it & the safe arrangement of it. In future it will be helpful for us

to choose the right gear among various types gear.

Page 21

Reference

5.1References

[1] FAIRES VIRGIL MORING, “DESIGN OF

MACHINE ELEMENTS”, 4th edition, The Macmillan

Company, New York/Collier-Macmillan Limited,

London

[2] Jain R.K., “ Production Technology”, 16th edition, 2-

B, Nath Market, Nai Sarak, Delhi-110006

[3]http://www.brighthubengineering.com/manufacturin

g-technology/7118-gear-manufacturing-methods

Page 22