Ipec lathe
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Transcript of Ipec lathe
LATHE MACHINE PROCESSES & OPERATIONS
Introduction
The lathe operates on the principle of the
work being rotated against the edge of a
cutting tool.
It is one of the oldest and most important
machine tools.
The cutting tool is controllable and can be
moved lengthwise on the lathe bed and into
any desired angle across the revolving work.
Types of Lathes
Speed
Simple construction of a head stock and tail stock
with a tool post. Used for wood turning, metal
polishing, or metal spinning.
Engine
Most frequently used lathe
Heavy duty
power drive for most tool movements
Size range 12”x24” to 24”x48” - can be larger
Types of Lathes (contd.)
CNC
Computer controlled
Wide variety of process capability
multiple axis
Indexing and contouring head
On- line and off- line programming available
CNC Lathe & Turret
Types of Lathes (contd.)
Toolroom
Greater accuracy
More versatility
Wider range of speeds and feeds
Capstan & Turret
Hex turret replaces tailstock
Multiple tools set to machine part
High production rates
Still may require some operator skill
Turret Lathe
Capable of performing multiple cutting operations on the same
workpiece
Turning
Boring
Drilling
Thread cutting
Facing
Turret lathes are very versatile
Types of turret lathes
Ram-type: ram slides in a separate base on the saddle
Saddle type:
more heavily constructed
Used to machine large workpeiceces
Turret Lathe
Difference between Capstan & Turret Lathe
Turret Lathe
Capstan Lathe
Types of Lathes (contd.)
Tracer Lathes
Machine tools with attachments
Capable of turning parts with various contours
A tracer finger follows the template and guides the cutting tool
Automatic Lathes
Automatic cutting off lathe
Single spindle automatic lathe
Swiss type automatic lathe, screw machines multiple spindle automatic lathes
Types of Lathes (contd.)
Automatic Bar Machines
Formerly called automatic screw machines
Designed for high-production-rate machining of screws and other
threaded parts
All operations are preformed automatically
Equipped with single or multiple spindles
Types of Lathes (contd.)
1
2
3
Lathe Size
Lathe size is determined by the SWING and LENGTH OF THE BED.
The swing indicates the largest diameter that can be turned over the
ways (flat or V-shaped bearing surface that aligns and guides movable
part of machine). Bed length is entire length of the ways.
Bed length must not be mistaken for the maximum length of the work
that can be turned between centers. The longest piece that can be
turned is equal to the length of the bed MINUS the distance taken up
by the headstock and tailstock.
As an example, consider the capacity and clearance of a modern 13 in
by 6 ft (325mm by 1800mm) lathe:
Swing over bed 13 in (325mm)
Swing over cross slide 8 3/4 in. (218mm)
Bed length 72 in. (1800mm)
Distance between centers 50 in. (1240mm)
Various Cutting Operations Turing – produces straight, conical, curved, or grooved
workpieces
Facing – produces a flat surface at the end of the part
Boring – to enlarge a hole
Drilling - to produce a hole
Cutting off – to cut off a workpeiece
Threading – to produce threads
Knurling – produces a regularly shaped roughness
Lathe Operations
Turning Operations
Schematic illustration of the basic turning operation, showing depth-of-cut, d; feed, f; and
spindle rotational speed, N in rev/min. Cutting speed is the surface speed of the
workpiece at the tool tip.
Summary of
Turning
Parameters
and
Formulas
Forces Acting on a Cutting Tool in Turning
Forces acting on a cutting tool in turning, Fc is the cutting force, Ft is the thrust of feed force (in the
direction of feed), and Fr is the radial force that tends to push the tool away from the workpiece
being machined.
Basic Turning Operations
Knurling
Standard Engine Lathe
Schematic of a standard engine lathe performing a turning operation, with the cutting tool shown in inset.
Engine Lathe Parts
Engine Lathe Parts
Lathe Design and Terminology
Lathe Engine essential
components:
Bed
Gray cast for vibration
dampening
Headstock assembly
Spindle
Transmission
Drive motor
Tailstock assembly
Longitudinal way clamp
Transverse way clamp
Quill for cutting tools,
live centers, or dead
centers
Schematic diagram of an engine lathe, showing basic components.
Lathe Design and Terminology
Lathe Engine essential components:
Quick-change gearbox
Powers Carriage Assembly movement with lead screw
Carriage Assembly
Fixed to cross slide
Holds tool post at variable orientations
Provides longitudinal and transverse movement of tooling
Ways
Provides precise guidance to carriage assembly and tailstock
Schematic diagram of an engine lathe, showing basic components.
Lathe Design and Terminology
Lathe Design and Terminology
Lathe Design and Terminology
Lathe Components
Lathe Components
Lathe Components
Lathe Components
BED
The bed of the lathe provides the foundation for the whole machine and holds
the headstock, tailstock and carriage in alignment. The surfaces of the bed
that are finely machined - and upon which the carriage and tailstock slide -
are known as "ways".
Some beds have a gap near the headstock to allow extra-large diameters to
be turned. Sometimes the gap is formed by the machined ways stopping
short of the headstock, sometimes by a piece of bed that can be unbolted,
removed and lost.
Some very large lathes have a "sliding bed" where the upper part, on which
the carriage and tailstock sit, can be slid along a lower separate part - and so
make the gap correspondingly larger or smaller.
SADDLE
The casting that fits onto the top of the bed and slides along it is known,
almost universally, as the "Saddle" - a self-explanatory and very suitable
term.
Lathe Components
APRON
The vertical, often flat and rectangular "plate" fastened to the front of the
"Saddle" is known as the "Apron" and carries a selection of gears and
controls that allow the carriage to be power driven up and down the bed -
and also engage the screwcutting feed and various powered tool feeds,
should they be fitted. The leadscrew, and sometimes a power shaft, usually
pass through the apron and provide it with a drive for the various functions it
has to perform.
Apron design can be roughly divided into "single-wall" and "double-wall"
types. The "single-wall" apron has just one thickness of metal and,
protruding from it (and unsupported on their outer ends) are studs that carry
gears. The "double-wall" apron is a much more robust structure, rather like a
narrow, open-topped box with the gear-carrying studs fitted between the two
walls - and hence rigidly supported at both ends
Lathe Components CROSS SLIDE and TOP SLIDE
Sitting on top of the "Saddle" is the "Cross Slide" - that, as its name implies,
moves across the bed - and on top of that there is often a "Top Slide" or
"Tool Slide" that is invariably arranged so that it can be swiveled and locked
into a new position.
Very early lathes had a simple T-shaped piece of metal against which the
turner "rested" his tool (all turning being done by hand) but when it became
possible to move this "Rest" across the bed by a screw feed it became
known, appropriately enough, as a "Slide-rest".
When two slides are provided (or sometimes, on watchmaker's lathes, three)
the complete assembly is known as a "Compound" or "Compound Slide" or
even "Compound Slide-rest". Some makers label the "Top Slide" as the
"Compound Rest" or even the "Compound Slide" - but as "to compound"
means the 'joining of two or more' - not 'one' - so this is not a correct use of
the term.
Lathe Components
CARRIAGE
The whole assembly of Saddle, Apron, Top and Cross Slide is known as the
"Carriage". Some American publications (even makers' handbooks) have
been known to casually refer to the "Saddle" as the "Carriage" - but this
incorrect.
HEADSTOCK.
The lathe Headstock used, at one time, to be called the "Fixed Headstock" or
"Fixed Head", and the rotating shaft within it the "Mandrel". Today the mandrel
is usually called the "Spindle", but this can cause confusion with the tailstock,
where the sliding bar is known variously as the "ram", "barrel" - and "spindle".
The headstock is normally mounted rigidly to the bed (exceptions exist in
some production and CNC lathes) and holds all the mechanisms, including
various kinds and combinations of pulleys or gears, so that the spindle can be
made to turn at different speeds.
Lathe Components
HEADSTOCK SPINDLE
The end of the headstock spindle is usually machined so that it can carry a
faceplate, chuck, drive-plate, internal or external collets - or even special
attachments designed for particular jobs. In turn, these attachments hold the
workpiece that is going to be machined.
BACKGEAR
As its name implies, "backgear" is a gear mounted at the back of the
headstock (although in practice it is often located in other positions) that
allows the chuck to rotate slowly with greatly-increased torque (turning
power).
Lathe Components LEADSCREW
Originally termed a "master thread", or described as the "leading screw", but now
always referred to as the "leadscrew", this is a long threaded rod normally found
running along the front of the bed or, on some early examples running between
the bed ways down the bed's centre line. By using a train of gears to connect the
lathe spindle to the leadscrew - and the leadscrew to the lathe carriage - the
latter, together with its cutting tool, could be forced to move a set distance for
every revolution of the spindle.
TAILSTOCK
The Tailstock was once known as the "Loose headstock", " Poppet head" or
"Loose head“. The unit is arranged to slide along the bed and can be locked to it
at any convenient point; the upper portion of the unit is fitted with what is variously
called a "barrel", "spindle" "ram" or "shoot" that can be moved in and out of the
main casting by hand, lever or screw feed and carries a "Dead Centre" that
supports the other end of work held (by various means) in the headstock.
Special centres, which rotate with the work, can be used in the tailstock ; these
are known as "Rotating Centres" and should not be referred to as "live centres" -
that term being reserved for the centre carried in the headstock spindle.
Cutting Tools for Lathes
Tools consists of cutting surface and support
Cutting surfaces can be of same material as
support or a separate insert
Supports materials must be rigid and strong
enough to prevent tool deflection during cutting
Cutting materials are typically carbides, carbide
coatings, ceramics, or high carbon steels
Inserts are used to decrease cost in that the insert
is disposed of, and the support reused.
Cutting Tools for Lathes
External
Right hand turning
Left hand turning
Round nose turning
Cut-off
Left hand facing
Cutting Tools for Lathes
External (con’t)
Broad nose finishing
Right hand facing
Threading
Form
Internal
Boring
Threading
Grooving
Form
Typical Tool Holders
FIGURE 22-16 Common
types of forged tool holders:
(a) right-hand turning,
(b) facing, (c) grooving cutoff,
(d) boring, (e) threading.
(Courtesy of Armstrong Brothers
Tool Company.)
Quick Change Tool Holders
Tool changing can take
over 50% of manual lathe
operations
Quick Change holders
are used to reduce
manual tool change time
and increase production
Workholding Devices for Lathes
Work pieces can be
held by various
methods
Work piece mounted
between centers
Work piece mounted
within a single chuck
Work piece mounted
within a collet
Work piece mounted on a
faceplate
Lathe Centers
A lathe center hold the end of the work piece, providing
support to preventing the work piece from deflecting
during machining
Lather centers can be mounted in the spindle hole, or in
the tailstock quill
Lathe centers fall into two categories
Dead Center: solid steel tip that work piece spins against
Live Center: centers contact point is mounted on bearings and
allowed to spin with work piece
Lathe Centers
FIGURE 22-21 Work being
turned between centers in a
lathe, showing the use of a dog
and dog
plate. (Courtesy of South Bend
Lathe.)
FIGURE 22-22 Live lathe
center can rotate with the part.
Lathe Chucks
Lathe Chucks are adjustable mechanical vises that hold
the work piece and transfer rotation motion from the
drive motor to the work piece
Lathe Chucks come in two basic types
Three-jaw self-centering chucks
Used to center round or hexagonal stock
Four-jaw independent chucks
Each jaw moves independently to accommodate various work piece
shapes
Lathe Chucks
The jaws on
chucks for lathes (four-jaw
independent or three-jaw selfcentering)
can be removed and
reversed.
Hydraulically
actuated through-hole three-jaw
power chuck shown in section
view to left and in the spindle of
the lathe above connected to
the actuator.
Face Plates
Mandrels
Lathe Collets
Collets are used to hold round stock of
standard sizes
Most accurate holding method for round
stock
Run out less than 0.0005 inch
Stock should be no more than 0.002 inch larger or
0.005 smaller than the collet
Typically used for drill-rod, cold-rolled, extruded,
or previously machined stock
Lathe Collets
FIGURE 22-26 Several types
of lathe collets. (Courtesy of
South Bend Lathe.)
Summary Lathes are used for turning, boring, drilling
and facing
Lathe typically holds the work piece in a
rotating chuck, with the opposite end
supported by a center held in the tailstock
A wide variety of lathe types, and tool types
are available depending upon the application
and the rate of production
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