ABSTRACT
This presentation is aimed at passing
across information on the lathe machine such as the various parts of the
machine, there function, and the uses of the machine.
INTRODUCTION
The center lathe is a machine tool, that is used to
remove unwanted material from a rotating work piece in form of chips with
the help of a tool which is transverse across the work and can be fed deep in
the work. The tool material should be harder than the work piece and the latter
held securely and rigidly on the machine. The tool may be given linear motion
in any direction.
Operation of center lathe machines are as follows.
•
1.Turning
•
2. Drilling
•
3.Facing
•
4.Producing of taper
•
5.Parting off etc.
SIZE OF
LATHE
The size
of lathe is specified in any of the following ways.
Ø The
height of the center measured over the lathe bed, or
Ø Swing or
maximum diameter that can be rotated over the bed ways.
Ø Swing or
maximum diameter over carriage. This is the largest diameter of work that will
revolve over lathe saddle.
Ø Maximum
job length in mm that may held between the canters [head stork and tail stork
centers.]
Ø Bed
length in meters which may include the head stock length also
Ø Diameter
of the hole through lathe spindle for turning bar material.
PARTS
OF LATHE
Ø BED: It is
supported on broad box section columns and is made of cat iron. Its upper
surfaces is either scraped or ground and the guiding and sliding surfaces are
provided. This bed consists of two heavy metal sliders running lengthwise, with
ways or vs. formed upon them. It is rigidly supported by cross girds. The outer
grids ways provides bearing and sliding surfaces for the carriage, and
the inner ways for the tailstock. This major units mounted on the bed are the
headstock, tailstock and carriage. The scraped or ground guiding and sliding
surfaces on the lathe bed ensure the accuracy of alignment of these three
units.
Ø HEAD STOCK: It
supports the main spindle in the bearings and aligns it properly. It also
houses necessary transmission mechanism with speed changing levers to obtain
different speeds
Ø MAIN SPINDLE: It is a
hollow cylindrical shaft and long slender jobs can pass through it. Facing the
tailstock is called the spindle nose. The spindle nose has no mores, taper hole
(self-locking taper) and threads on outside. The Morse, taper is used to
accommodate lathe center or collect clock and threads portion for clock or face
plate.
Ø TAIL STOCK: It is a
movable casting located opposite the headstock on the ways of the bed. It is
used for two purposes,
q to
support the other end of the work when being machined and
q to
hold a tool for performing operations like drilling, reaming, tapping
etc.
The body of the tailstock is adjustable on the base and can be moved to and
fro. The object of making the body adjustable on the base is to provide means
for lining up the centre, carried in the moving spindle, with the headstock
centre or for offsetting this centre to permit tapers to be turned.
Ø CARRIAGE: It is
located between the headstock and the tailstock. It is fitted on the bed and
slides along the bed guide ways and can be locked on the bed at any desired
position by tightening the carriage lock screw. It can be moved manually with a
hand wheel or with power feed. It consists of the following main parts.
•
saddle.
•
cross
slide
•
compound rest consisting of a swivel and top slide
(iv) tool
post
apron.
Ø APRON: It is
fastened to the saddle and hangs over the front of the bed. It controls the
gears and clutches for transmitting motion from the feed rode to the carriage
and the split nut which engages with the load screw during cutting threads. It
converts the rotary motion of the feed shaft or the load screw to a translating
motion of the carriage longitudinally on the lathe bed or the cross slide
transversely on the carriage.
Ø SADDLE: It is
made up of a H shaped casting. Generally it has a V guide and a flat guide on
one side for moving it on the lathe bed guide ways. It also aids the saddle to
slide along the bed guide ways by operating a hard wheel. The other side of
saddle is provided with a male dove tail to accommodate the cross slide with a
jib
ACCESSORIES
OF LATHE
Ø FACE
PLATE: Mounting work on a face plate provides an ideal way of supporting
certain types of works. Flat plates may be screwed to the face plate for
operations such as facing, drilling and boring. If the work has several holes,
it most be about each successive hole.
Ø CENTERS: Lathe
centre are used for work holding during turning operation. A centre hole of
particular depth and shape is made at each end of the work piece. The lathe
centre act as supports for the work piece and take up the thrust due to metal
cutting. The included angles of centre is 60 ̊ for general purpose work
and 75 ̊ for heavy work. we have the live or revolving centre and dead
centre. The revolving centre is used for supporting heavy jobs revolving at
high speed.
Ø STEADY
REST: The steady rest is used when a long piece is machined or drilled at its
end by holding the job in a clock. It avoids the undue deflection of the job at
the other end.
Ø COMPOUND REST: It
support the tool post and cutting tool on its various post. It may be swiveled
on the cross-slide to any angle in the horizontal plane base being graduated
suitably. A compound rest is necessary in boring, short tapers, and in turning
angles and forms on forming tools.
Ø CROSS SLIDE: It is
provided with a female dove tail on one side and assembled on the top of the
saddle with its male dove tail. A tapered gib is provided between the saddle
and cross slide dove tail to permit required fit for movement of cross
slide on saddle. Top surface of top cross slide is provided with T knots to enable
fixing of rare rod post or coolant attachment. Front side is graduated in
degrees to facilitate swiveling of the compound rest to the desired angle.
Ø TOOL POST: It is
used to hold various cutting holders, these holders rest on the wedge which is
shaped on the bottom to fit into a concave shaped ring which permit the height
of the cutting edge to adjusted by tilting the tool. It is fixed on the top
slide. It gets its movement by the movement of the saddle, cross slide and top
slide
Ø FOLLOW REST:A follow
rest performs the same function as a steady rest, but it is attached to the
saddle and moves along with the tool. It thus supports the work opposite to the
tool and counteracts the cutting forces.
Ø CHUCK: It is
the most important device for holding the work piece, particularly of short
length and large diameter or of irregular shape which cant be conveniently
mounted between centre. It can be attached to the lathe by screwing on the
spindle nose. Types of
chucks;
(a) Independent or four jaw chuck: It has four jaws and each jaw is
independently and adjusted. This type of jaws is used for irregular shapes, in
jobs when a hole is to be positioned of the
centre.
(b) Three jaw or universal chuck: In this case, all the three jaws move
simultaneously by turning a key and thus the work piece may be automatically
held in the center of chuck opening. It is used for holding round hexagonal bar
or other symmetrical work.
DOG: The dog is normally used in
conjunction with the face plate to securely clamp the work on the live center
end. The work turns with the live centre which acts both as a support and
a bearing.
TAPER TURNING ATTACHMENT: This attachment is confined to give
external and internal tapers . It is bolted on the back of the lathe and has a
guide bar which may be set at the desired angle of taper. As the carriage moves
along the bed length, a slide over the bar causes the tool to move in out
according to the setting on the bar i.e. the taper setting of the bar is
duplicated on the work. The main advantage of this system is that the lathe
centre are kept in alignment and the same taper may be turned on various
pieces even though they vary in length.
SAFETY ON LATHE MACHINE
Ø You must know the on and
off.
Ø Rings and wrist watches
should not be worn.
Ø Safety boot must be worn.
Ø Loose wares are not
allowed as they may caught in the machine.
Ø Stop the machine before
cleaning or measuring.
Ø Keep hands off moving
parts.
Ø Never wear gloves when
operating a machine.
Ø Long hair most be well
protected by a hair net.
SCHAMATIC
SKETCH OF LATHE
PARTS
•
Head stock
•
Spindle
•
Tool post
•
Gap bed
•
Compound slide
•
Cross slide
•
Tail stock
•
Bed
•
Saddle
REFERENCES-
Production Technology, By R.K Jain.
04:54:00
