What is lathe machine ?
Introduction
The lathe is one of the oldest machine tools. and come into existence form the early tree lathe which was then a novel device for rotating and machining a piece of work held between two adjacent trees. A rope wound round the work with its one end attached to a flexible branch of a tree and the other end being pulled by a man caused the job to rotate intermittently .Hand tools were then used .With its further development a strip of wood called "lathe" was used to support the rope and that is how the machine came to be known as "lathe".
The types generally used are:
1. Speed lathe 3. Bench lathe .
(a) Wood working 4. Tool room lathe.
(b) Centering 5. Capstan and Turrret lathe.
(c) Polishing 6. Special purpose
(d) Spinning (a) Wheel lathe.
(b) Gap bed lathe
2. Engine lathe. (c) T-lathe
(a) Belt drive (d) Duplicating lathe.
(b) Individual motor drive 7. Automatic lathe.
(c) Gear head lathe.
The size of a lathe is expressed or specified by the following items and illustrated in
1. The height of the centres measured from the lathe bed.
2. The swing diameter over bed. This is the largest diameter of work that will revolve without touching the bed and is twice the height of the center measured from the bed of the lathe.
3. The length between centres. This is the maximum length of work that can be mounted between the lathe centres.
4. The length of bed .This indicates the approximate floor space occupied by the lathe.
Illustrates the basic parts of a geared head lathe. Following are the principal parts:
1. Bed 4.Carriage
2. Headstock 5. Feed mechanism
3. Tailstock 6. Screw cutting mechanism
(a) It should be sufficiently rigid to prevent deflection under tremendous cutting pressure transmitted through the tool-post and carriage to the lathe bed.
(b) it must be massive with sufficient depth and width to absorb vibration.
(c) The bed should be seasoned naturally to avoid distortion or warp that may develop when it is cooled after the bed is cast.
The spindle of the headstock illustrated in is made of carbon or nickel-chrome steel.This is usually of a large diameter to resist bending and it should be perfectly aligned with the lathe axis and accurately machined for producing true work surface.A hole extends through the spindle so
that a long bar may be passed through the bore.The front end of the hole is appeared for holding
centres and other tools having a standard Morse taper shank.A taper sleeve fits into the taper hole,
and a live centre which supports the work and revolves with the work fits into the sleeve that acts
as a bush.There are common types of spindle noses: the threaded design which carries the chuck,
driving plate and face plate and the flanged nose which enable them to be directly attached.The
lathe most commonly used has a threaded spindle nose.
The spindle revolves on two bearings housed on the headstock casting. The clearance between the spindle and the bearing should be minimum to prevent vibration .The bearing may be either
bush,ball or roller type depending on whether it is a high speed , heavy duty or precision
machine .Thrust bearings are provided to take up the end load owing to the feeding action of the
tool. Provision is made for expansion of the spindle when it gets heated under high speed metal
cutting .
(1) it supports the other end of the work when it is being machined between centres and
(2) it holds a tool for performing operation such as drilling ,reaming,tapping etc
consists of the following parts:
(1) saddle (2) cross-slide (3) compound slide or compound rest
(4) tool post, and (5) apron. A sectional view of the carriage
of feed-longitudinal ,cross, and angular.When the tool moves parallel to the lathe axis the
movement is termed as the longitudinal feed and is effected by the movement of the carriage .
When the tool moves at the right angel to the lathe axis with the help of the cross slide the
movement is termed as cross feed,While the movement of the tool by compound slide when it is
swivelled at an angle to the lathe axis is termed as angular feed. Cross and longitudinal feed ate
both hand and power operated ,but angular feed is only hand operated .
The feed mechanism has different units through which motion is transmitted from the headstock
spindle to the carriage .Following are the untis
1. End of bed gearing
2. Feed gear box
3 Feed rod and lead screw
4 Apron mechanism
In order to perform different machining operation in a lathe,the workpiece may be supported and driven by any one of the following
Pdn
cutting speed = ------------- m / min
1000
D __ D
1 2
Depth of cut = ---------------------
2
Where, D = diameter of the work surface before machining
1
D = diameter of the machined surface
2
The machining time in lathe work can be calculated for a particular operation if the speed of the job feed length of the job is known :
If a is the feed of the job per revolution expressed in mm per revolution and l the length of the job in mm then number of revolution of the job required for a complete cut will be :
If the r.p.m. of the work is n , time taken to revolve the job through l/s number revolution for a complete cut will be :
l
---------
S × N l
Therefore the time taken for a complete cut = ------------ min.
S × N
This article was taken by
S.K. Hajra choudhury
A.K. Hajra choudhury
Function of the lathe
The main function of a lathe is to remove metal from a piece of work to give it the required shape and size.This is accomplished by holding the work securely and rigidly on the machine and then turning it against cutting tool which will remove metal from the work in the from of chips .To cut the material properly the tool should be harder than the material of the workpiece ,should be rigidly held on the machine and should be fed or progressed in a definite way relative to the work.Types of lathe
Lathe of various designs and constructions have been developed to suit the various conditions of metal machining .But all of them employ the same fundamental principle of operation and perform the same function.The types generally used are:
1. Speed lathe 3. Bench lathe .
(a) Wood working 4. Tool room lathe.
(b) Centering 5. Capstan and Turrret lathe.
(c) Polishing 6. Special purpose
(d) Spinning (a) Wheel lathe.
(b) Gap bed lathe
2. Engine lathe. (c) T-lathe
(a) Belt drive (d) Duplicating lathe.
(b) Individual motor drive 7. Automatic lathe.
(c) Gear head lathe.
The size of lathe
The size of a lathe is expressed or specified by the following items and illustrated in
1. The height of the centres measured from the lathe bed.
2. The swing diameter over bed. This is the largest diameter of work that will revolve without touching the bed and is twice the height of the center measured from the bed of the lathe.
3. The length between centres. This is the maximum length of work that can be mounted between the lathe centres.
4. The length of bed .This indicates the approximate floor space occupied by the lathe.
DESCRIPTIOINS AND FUCTIONS OF LATHE PARTS
Illustrates the basic parts of a geared head lathe. Following are the principal parts:
1. Bed 4.Carriage
2. Headstock 5. Feed mechanism
3. Tailstock 6. Screw cutting mechanism
1. The Bed
The lathe bed forms the base of the machine .The headstock and the tailstock are located at either end of the bed and the carriage rests over the lathe bed and slides on it. the lathe bed being the main guiding member of the tool,for accurate machining work, must satisfy the following conditions:(a) It should be sufficiently rigid to prevent deflection under tremendous cutting pressure transmitted through the tool-post and carriage to the lathe bed.
(b) it must be massive with sufficient depth and width to absorb vibration.
(c) The bed should be seasoned naturally to avoid distortion or warp that may develop when it is cooled after the bed is cast.
2. The Headstock
The headstock is secured permanently on the innerways at the left hand end of the lathe bed and it provides mechanical means of rotating the work at multiple speeds. It comprises essentially a hollow spindle and mechanism for driving and altering the spindle speed. All the parts are housed within the headstock casting.The spindle of the headstock illustrated in is made of carbon or nickel-chrome steel.This is usually of a large diameter to resist bending and it should be perfectly aligned with the lathe axis and accurately machined for producing true work surface.A hole extends through the spindle so
that a long bar may be passed through the bore.The front end of the hole is appeared for holding
centres and other tools having a standard Morse taper shank.A taper sleeve fits into the taper hole,
and a live centre which supports the work and revolves with the work fits into the sleeve that acts
as a bush.There are common types of spindle noses: the threaded design which carries the chuck,
driving plate and face plate and the flanged nose which enable them to be directly attached.The
lathe most commonly used has a threaded spindle nose.
The spindle revolves on two bearings housed on the headstock casting. The clearance between the spindle and the bearing should be minimum to prevent vibration .The bearing may be either
bush,ball or roller type depending on whether it is a high speed , heavy duty or precision
machine .Thrust bearings are provided to take up the end load owing to the feeding action of the
tool. Provision is made for expansion of the spindle when it gets heated under high speed metal
cutting .
3. TAILSTOCK
The tailstock is located on the innerways at the right hand end of the bed, this has two main uses :(1) it supports the other end of the work when it is being machined between centres and
(2) it holds a tool for performing operation such as drilling ,reaming,tapping etc
4. CARRIAGE
The carriage of a lathe has several parts that serve to support move and control the cutting tool ,Itconsists of the following parts:
(1) saddle (2) cross-slide (3) compound slide or compound rest
(4) tool post, and (5) apron. A sectional view of the carriage
5 FEED MECHANISM
The movement of the relative to the work is termed as "feed" .A lathe tool may have three typesof feed-longitudinal ,cross, and angular.When the tool moves parallel to the lathe axis the
movement is termed as the longitudinal feed and is effected by the movement of the carriage .
When the tool moves at the right angel to the lathe axis with the help of the cross slide the
movement is termed as cross feed,While the movement of the tool by compound slide when it is
swivelled at an angle to the lathe axis is termed as angular feed. Cross and longitudinal feed ate
both hand and power operated ,but angular feed is only hand operated .
The feed mechanism has different units through which motion is transmitted from the headstock
spindle to the carriage .Following are the untis
1. End of bed gearing
2. Feed gear box
3 Feed rod and lead screw
4 Apron mechanism
6. Screw cutting mechanism
LATHE OPERATION
In order to perform different machining operation in a lathe,the workpiece may be supported and driven by any one of the following
1. CUTTING SPEED
The cutting speed (v) of a tool is the speed at which the metal is removed by the tool from the workpiece .In a lathe it is the peripheral speed of the work past the cutting tool expressed in meters per minute.Pdn
2. DEPTH OF CUT
The depth of cut (t) is the perpendicular distance measured from the machined surface to the uncut surface of the workpiece .In a lathe the depth of cut is expressed as follows :D __ D
1 2
Depth of cut = ---------------------
2
Where, D = diameter of the work surface before machining
1
D = diameter of the machined surface
2
3. MACHINING TIME
The machining time in lathe work can be calculated for a particular operation if the speed of the job feed length of the job is known :
If a is the feed of the job per revolution expressed in mm per revolution and l the length of the job in mm then number of revolution of the job required for a complete cut will be :
If the r.p.m. of the work is n , time taken to revolve the job through l/s number revolution for a complete cut will be :
l
---------
S × N l
Therefore the time taken for a complete cut = ------------ min.
This article was taken by
S.K. Hajra choudhury
A.K. Hajra choudhury
thanks for this usefull article, waiting for this article like this again. AI MI electric actuator
ReplyDeleteHi there to everybody, it’s my first go to see of this web site; this weblog consists of awesome and in fact good stuff for visitors. Hurrah, that’s what I was exploring for, what stuff! Existing here at this blog, thanks admin of this web site. You can also visit Metal Machining Parts for more aludiecasting related information and knowledge.
ReplyDeleteAwesome article, it was exceptionally helpful! I simply began in this and I'm becoming more acquainted with it better! Cheers, keep doing awesome! water bottle filling stations
ReplyDeleteI don’t think many of websites provide this type of information. fiber laser cutting machine for metals
ReplyDeleteIntroducing seven innovated power tools and a worklight, Dewalt's 20V MAX line is complete, comprehensive and focused on operator comfort and convenience. best pole saws
ReplyDelete