Lathe Machine is a Production Machine tool. Here today we will study Definition, Parts, Operation, Specification of Lathe Machine.
You can download the whole document in a PDF format, I will add the PDF download link at the bottom of this article.
So let me give you the introduction of the lathe machine tool.
Lathe machine introduction
The Lathewas invented by Jacques de Vaucanson around 1751.
The Lathe Machine is an ancient tool. At the very early stage this machine was developed around 1300 BC at that time there was not developed so many parts expect headstock and Tailstock. But during the industrial revolution Metalworking lathe evolved into heavier machines with thicker, more rigid parts.
Between 19 and 20 centuries the electric motor is replaced line shafting as a power source.
Then in 1950, the servomechanism is applied to control lathe and other machine tools by numeric, Direct numerical control machine.
The Lathe is the most versatile machine tool among all standard of the machine tool.
Nowadays the manually controlled machine exists like a CNC machine and even do with the help of feed mechanism the lathe machine operates manually.
Lathe Machine Definition:
A lathe machine is a machine tool that is used to remove metals from a workpiece to give a desired shape and size.
Lathe Machines are used in metalworking, woodturning, metal spinning, thermal spraying, glass working, and parts reclamation.
The various other operations that you can perform with the help of Lathe Machine can include sanding, cutting, knurling, drilling, and deformation of tools that are employed in creating objects which have symmetry about the axis of rotation.
There are several components of a lathe, later on, I discuss the most important Parts of Lathe with their function. It is also known as the father of all standard machine tools.
The function of Lathe is to remove the metal in the form of chips from a piece of work by mounting the same rigidly on a machine spindle and revolving at the required speed and the cutting tool is fed against the work either longitudinally or crosswise to make the work to the required shape and size.
Parts of the Lathe Machine and their functions:
So what are the Parts of a Lathe machine? A lathe machine tool consists of several parts like:
Let me explain all these parts in detail.
Head Stock is situated at the left side of the lathe bed and it is the house of the driving mechanism and electrical mechanism of a Lathe machine tool.
It holds the job on its spindle nose having external screw threads and internally Morse taper for holding lathe center. And it is rotating at a different speed by cone pulley or all geared drive. There is a hole throughout spindle for handling long bar work.
Head Stock transmit power from the spindle to the feed rod, lead screw and thread cutting mechanism.
Accessories mounted on headstock spindle:
Three jaw chuck
Four jaw chuck
Lathe center and lathe dog
A separate speed change gearbox is placed below headstock to reduce the speed in order to have different feed rates for threading and automatic lateral movement of the carriage. The feed rod is used for most turning operation and the lead screw is used for thread cutting operation.
It is the base of the lathe machine. It is made of single piece casting of Semi-steel ( Chilled Cast Iron). The bed consists of two heavy metal slides running lengthwise, with ways or 'V' formed upon them and rigidly supported with cross girths.
It is sufficiently rigid and good damping capacity to absorb vibration.
It prevents the deflection produced by the cutting forces.
It supports the headstock, tailstock, carriage and other components of the lathe machine.
Tail Stock is situated on the right side above the lathe bed.
It is used for:
Support the long end of the job for holding and minimizes its sagging.
It holds the tool for performing different operations like drilling, reaming, tapping, etc.
And it is also used for a small amount of taper for a long job by offsetting the tailstock.
The carriage is used for support, guide and feed the tool against the job when the machining is done.
It holds moves and controls the cutting tool.
It gives rigid supports to the tool during operations.
It transfers power from feed rod to cutting tool through apron mechanism for longitudinal cross-feeding.
It simplifies the thread cutting operation with the help of lead screw and half nut mechanism.
It is consists of:
It provides three movements to the tool:
Longitudinal feed-through carriage movement
Cross feed-through cross slide movement
Angular feed-through top slide movement
Generally, it is made up of 'H' shaped casting and it has a 'V' guide and a flat guide for mounting it on the lathe bed guideways.
It is assembled on the top of the saddle. The top surface of the cross-slide is provided with T-slot.
It supports the tool post and cutting tool in its various positions. It can be swiveled at any desired position in the horizontal plane. It is necessary for turning angles and boring short tapers.
It is the topmost portion of the carriage and it is used to hold various cutting tools or tool holders.
There are three types of tool post commonly used and those are:
Ring and rocker tool post
Squarehead tool post
Quick change tool post
An apron is a house of the feed mechanism. It is fastened to the saddle and hangover in front of the bed.
A lead screw is also known as a power screw or a translation screw. It converts rotational motion to linear motion. Lead Screw is used for Thread Cutting operation in a lathe machine tool.
Feed rod is used to move the carriage from the left side to the right side and also from the right side to the left side.
Chuck is used to holding the workpiece securely.
There are generally 2 types of chucks:
3 jaw self-centering chuck
4 jaw independent chuck
The spindle is a hollow cylindrical shaft in which long jobs can pass through it.
It is designed so well that the thrust of the cutting tool does not deflect the spindle.
Legs are carrying an entire load of a lathe machine tool and transfer to the ground. The legs are firmly secured to the floor by the foundation bolt.
Schematic diagram of the lathe machine:
Types of Lathe Machine
Lathe machine tool which is used for removing the excess material from the workpiece to give required shape and size to the workpiece.
So how many types of Lathe Machine are there? Lathe machine has been categorized into the following types:
Center or Engine Lathe
Capstan and Turret Lathe
Tool Room Lathe
Special Purpose and
CNC Lathe Machine
We are going to study each and every important point of these 8 different types of lathe machines.
Center or Engine Lathe Machine:
Center or Engine Lathe Machine is the most widely used lathe machine and still, it is, in every workshop, this machine is present.
The operation like Turning, facing, grooving, Knurling, threading and more, such operations are performed on this type of machine.
Engine lathe machine has all the parts such as bed, Saddle, headstock, and tailstock, etc. The headstock of an engine lathe is rigid and tailstock is moveable which is further used to support an operation like knurling.
It can easily feed the cutting tool in both directions i.e. longitudinal and lateral directions with the help of feed mechanisms.
Center Lathe machines are driven by the gear mechanism or pulley mechanism.
It has three types of driven mechanisms, and those are Belt-driven, Motor-driven, Gearhead type.
As the name indicates “Speed” the machine works with high speed. The headstock spindle is rotating at a very high speed. The parts having like headstock, tailstock, but it's not having feed mechanism like center or engine lathe having. The feed we provide is manually operated.
The speed ranges of this machine operated between 1200 to 3600 RPM.
Speed lathe is used for spinning, centering, polishing and machining of wood.
Capstan and Turret Lathe:
This is an advanced technology of the manufacturing industry.
The capstan and turret lathe machine used for Mass production (large Quantity) and it is a modified version of the engine lathe machine.
This machine is used where their sequence of operation is performed on the workpiece, there is no alternative operation performed on this machine.
These machines provided by hexagonal turret head instead of the tailstock in which multiple operations (Turning, facing, boring, reaming) performed in a sequence without changing its tool manually, after each operation the turret rotated.
It also consists of three tool post. It requires more floor space than other lathe machines.
Capstan and turret lathe is using for only large jobs.
The main advantage of using capstan and turret lathe is even less skilled operators can do a job.
Tool Room Lathe:
The toolroom lathe machine operates to speed up to 2500 rpm.
The parts are almost the same similar to engine lathe machine but the parts are built very accurately and should be arranged in proper sequence because this lathe is used for highly precious work with very fewer tolerances.
It is mainly used in grindings, working on the tool, dies gauges and in machining work where accuracy is needed.
Bench lathe machines are mounted on the bench.
This type of lathe machine is small in size and use for very small precision work. It has all the similar parts of engine lathe and speed lathe.
As the name indicates “Automatic lathe” performs work automatically.
Standard lathes have some drawbacks i.e. they are not used for mass production. But automatic lathes are used for mass production. Some mechanisms are responsible for the automation in it.
Here there is no need to change the tool manually because it changes automatically.
Having this machine the main advantage is that a single operator can handle machines more than 4 to 5 machines at a time.
These types of lathes are high speed and heavy-duty.
Special Purpose Lathe:
As the name indicates “special purpose lathe” the machine performs the special types of operation which can not be performed on standard and other machines.
It is known for the heavy-duty production of identical parts.
Some examples of special lathes include Vertical lathes, Wheel lathes, T-lathe, Multi Spindle lathes, Production lathes, Duplicate or tracer lathes, etc.
Wheel lathe is used for machining of journals and rail rods. It is also used for turning the threads on locomotive wheels.
The “T -lathe” is used for machining rotors for jet engines. The axis of the lathe bed is at right angles to the axis of the headstock spindle in the form of a T.
CNC Lathe Machine:
CNC stands for Computerized numerically controlled.
This is widely used as a lathe in the present time because of its fast and accurate working. It is one of the most advanced types.
It uses computer programs to control the machine tool. Once the program is fed into the computer as per the program it starts operation with very high speed and accuracy.
Even do preplanned programmed machine is there in which once code is set for the various operations it can starts operation without changing code in the next time.
A semi-skilled worker can easily operate this after the initial setup is done.
These types of lathes are also used for mass production like capstan and turret but there is no programmed fed system.
The components manufactured by these lathes are very accurate in dimensional tolerances.
Now discuss the operations performed in a Lathe
A Lathe Machine consists of the following operation:
Before continuing any operation in lathe we have to load the job and center it on the head-stock spindle.
In lathe operations, the headstock spindle holds the job and it rotates with the same speed as the spindle. The carriage holding the tool on the tool post, also the carriage gives the tool post moves longitudinally or crosswise direction to give the desired feed on the job.
These two motions (longitudinally and crosswise) helps to remove the chips of the metal and giving the proper shape of the job.
The Lathe is such a versatile machine that it can produce another lathe.
It is tough to mentioned which operations are not performed in a lathe machine tool, though we discuss some important lathe operations in detail.
Centering operation in the lathe:
We use this operation for producing a conical hole in the face of the job to make the bearing support of the lathe center when the job is to hold between two centers. (Head-stock and Tail-stock).
Facing operation in the lathe:
Facing operation is for making the ends of the job to produce a smooth flat surface with the axis of operation or a certain length of a job.
In this operation,
Hold the job on Head-stock spindle using Three or four-jaw chuck.
Start the machine on desire RPM to rotate the job.
Give a desirable feed on the perpendicular direction of the axis of the job.
Turning operation in the lathe:
The operation by which we remove the excess material from the workpiece to produce a cone-shaped or a cylindrical surface.
There are several types of turning operations, those are:
This operation is done to produce a cylindrical surface by removing excess material from the workpiece.
It is done in the following ways:
Mount the job by suitable job holding device and check the trueness of the job axis with the lathe axis.
Hold the cutting tool on the tool post and set the cutting edge at the job axis or slightly above it.
Set the spindle as per the desired feed.
Give depth of cut as per finish or rough cut.
Start the machining.
Engage automatic feed to move the carriage with the tool to the desired length, then disengage the feed and carriage is brought back to its starting.
The process is repeated until the job finished.
A shoulder turning is called which has a different diameter to form a step from one diameter to another.
There are four kinds of the shoulder.
It is a process of removal of excess material from the workpiece in minimum time by applying a high rate of feed and heavy depth of cut.
the depth of cut is around 2 to 5mm and the rate of feed is 0.3 to 1.5mm/revolution.
The finish turning operation needs high cutting speed, minimum feed and a very small depth of cut to generate the smooth surface.
In finish turning the depth of cut is around 0.5 to 1mm and the rate of feed is 0.1 to 0.3 mm/revolution.
First, let me give you an idea about the taper.
A taper is defined as a uniform decrease or increase in the diameter of a workpiece along with its length.
The operation by which a conical surface of the gradual reduction in diameter from a cylindrical workpiece is produced is called taper turning.
Taper turning methods:
A tapering form may be done by anyone of the following methods.
Taper turning by form tool
By swiveling the compound rest
Tail-stock set over method
By taper turning attachment
Let me discuss them in brief.
Taper turning by form tool:
It is used to form a short length of taper by using a form tool or broad nose tool.
Any increase in the length of taper will require the use of a wider cutting edge which may destroy the workpiece due to the vibration and spoil the workpiece.
In this operation, the tool angle must be half of the taper angle.
Taper turning by swiveling the compound rest:
This method is used for turning step and short tapers.
It is done as follows:
Set the compound rest by swiveling it from the centerline of the lathe center through an angle equal to a half taper angle.
Clamp the carriage in place.
After adjusting and setting the tool, feed is applied by the compound rest's feed handle to complete the taper.
Tail-stock set over method:
Set over of tail-stock from its center-line is done equal to half taper.
Job is held between the centers. The length of the workpiece will be long enough. An only a small taper on a long job is done by this process.
It is used for external taper only.
By taper turning attachment:
It is done in the following ways:
The cross slide is first made free from lead screw by hinder screw.
The rear end of the cross slide is then tightened with a guide block by a belt.
Set the guide bar at an angle to the lathe axis. (Half taper angle)
The required depth of cut is given by the compound slide is at a right angle to the lathe axis.
Chamfering is used for beveling the end of a job to remove burrs, to look better, to make a passage of the nut into the bolt.
This operation is done after thread cutting, knurling, rough turning.
It is the process of producing a rough surface on the workpiece to provide effective gripping.
Knurling tool is held rigidly on the tool post and pressed against the rotating job so that leaving the exact facsimile of the tool on the surface of the job.
Thread cutting operation :
It is the operation that is used to produce a helical groove on a cylindrical or conical surface by feeding the tool longitudinally when the job revolved between the two centers.
Tool setting for thread cutting operation:
The tool should be set exactly to the height of the centerline of the job and at 90 degrees to the job.
Tool setting gauge is used for this purpose.
Feeding during thread cutting operation:
It is done in two ways.
The tool may be feed exactly at 90 degrees to the job axis but it does not have good cutting action because only the front end of the tool does cutting.
The tool may be feed at an angle from 27-30 degrees at which the compound rest may be set so that the complete side of the tool is used for cutting action which gives a better polish on the threads.
Job speed during threading:
The job speed will be 1/3 to 1/4 th of the job speed in turning operation.
Drilling is an operation by which we can make holes in a job.
In this operation, the job is rotated at the turning speed on the lathe axis and the drilling tool fitted on the tail-stock spindle. And the tail-stock is moved towards the job by hand feed.
In this operation, we can enlarge the diameter of the existing hole on a job by turning inside with some farm tool known as a boring tool.
The boring tool is also fitted on tail-stock.
Reaming is the operation for sizing or finishing a drilled hole to the required size by a tool called reamer.
This tool is fitted on tail-stock.
In this operation, the job of this sheet metal is held between the former and the tail-stock center rotates at high speed with the former.
the long round nose forming tool rigidly fixed on special tool post presses the job on the periphery of the former. So the job is taken exactly the shape of the former.
This is a chipless machining process.
We use this operation for creating internal threads within a hole by means of a tool called tap.
Three taps are generally used in an internal thread.
It is the operation of cutting off a bar type job after complete the machining process.
In this operation a bar type job is held on a chuck, rotates at turning speed, a parting off tool is fed into the job slowly until the tool reaches the center of the job.
Specification of a Lathe:
A Lathe is generally specified by:
Swing- the largest work diameter that can be swung for the lathe bed.
The distance between the headstock and tailstock center.
Length of the bed in a meter.
The pitch of the lead screw.
Horsepower of the machine.
Speed range and the number of speeds of HS spindle.
If you have any queries or doubts about the lathe machine tool, you can ask me in the comment section and also you can join our facebook group. I will love to hear from you and glad to help you. Till then enjoy rest your day. Cheers
What are the different types of lathe operations?
A lathe is a versatile machine tool, you can perform almost any operations but in general, we use the lathe for turning, facing, chamfering, learning, thread cutting, drilling, boring, reaming, etc.
Who invented lathe?
David Wilkinson, a US-based mechanical engineer in the early 19 century invented lathe machine tools.
What are the different types of taper turning methods in Lathe?
There generally 4- types of taper turning method, those are taper turning by form tool, by swiveling the compound rest, tail-stock set over method and taper turning attachment.
What are the different types of turning?
There are 6- types of turning and those are straight turnings, shoulder turning, rough turning, finish turning, taper turning, eccentric turning.
Can I perform drilling operations in a lathe?
Yes, of course. You can perform drilling as well as reaming, boring operations using tailstock.
Is it necessary to do centering operation before performing any operation in lathe?
Yes, it is. Otherwise, your alignment will be wrong, and the job, as well as tool, maybe wear out.
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