A lathe machine is a machine tool used to rotate various workpieces about one axis to perform operations like facing, turning, cutting, taper turning, knurling, drilling, etc to make a finished object. In a lathe machine, various individual parts are contributing or in action to give you a finished product. Here are the parts of lathe machine with its description, construction, and its working.
Parts of lathe machine
- Lathe Bed
- Cross Slide
- Compound rest
- Tool post
- Lead Screw
- Feed Rod
- Thread cutting mechanism
- Chip Pan
- Gear box
- Cooling Devices
Parts of lathe machine with diagram
1. Lathe Bed
The lathe bed is the rigid and strong part of the lathe machine. It is generally made of cast iron because it is hard and absorbs vibrations. It avoids deflection due to a heavy working load.
The headstock locates on the left side, and the tailstock is on the right side of the bed. The carriage rests on the bed and slides over the bed.
On the top of the lathe bed, guideways are there to slide tailstock and carriage over it. These guideways are accurately machined to make them parallel with each other and provide bearing and sliding surfaces to tailstock and carriage to slide. It is high resistance to wear.
There are two types of guideways.
- Flat guideways
- Inverted V guideways
Flat guideways give a high bearing surface, minimum wear, and are easy to clean. And inverted V guideways give better alignment and a better guide to tailstock and carriage. It helps to fall down the chips from the bed.
Headstock fixes on the left-hand side of the lathe bed. It helps to rotate different workpieces at different speeds with the help of chuck. Spindle, chuck, gears, gear drive, speed, and feed selector are present inside the headstock casting.
The material of the spindle is nickel or carbon chrome steel. The centreline of the spindle and centreline of the lathe are perfectly in alignment with each other.
It is hollow from the inside so, a long bar can pass through it. The front end of the spindle can hold the taper part.
There are two types of spindles.
The threaded design carries a driving plate, faceplate, and chuck, whereas a flanged one enables them to attach.
The spindle is guided with the two bearings from both sides in the headstock. It can be a ball, bush, or roller bearing. The selection of bearings depends on the type of application, loads, speed, and accuracy.
Chuck is for holding the workpiece during the machining process. It can be able to hold workpieces of irregular shapes rigidly and quickly. Chuck is attached to the backplate with bolt, and the backplate is screwed to the spindle nose. It is necessary to have an accurate alignment of the chuck with the lathe axis.
Different types of chucks
Four Jaw Chuck-
Four jaw chuck has four jaws that slide in the slot to give good gripping for different shapes of workpieces. In some cases, each jaw can slide independently by rotating a screw.
With the chuck, we can clamp hollow parts from inside and from outside as well. Gripping surfaces of four jaws simultaneously apply pressure on the outside diameter of the pipe for clamping. Whereas, for clamping from inside, outer gripping surfaces simultaneously apply pressure on inside surfaces of the pipe.
Three Jaw Universal Chuck-
Universal chuck consist of three jaws simultaneously slides in the slot to clamp the workpieces. We can reduce the distance from three jaws by rotating the key in the slot in the chuck.
This chuck is suitable for providing quick grip in the round, hexagonal, and similar shapes. It has less gripping capacity than four jaw chuck.
Air or Hydraulic operated Chuck-
It consists of a hydraulic or compressed air cylinder mounted on the backside of the headstock. During the clamping acting, hydraulic oil or compressed air is forced through the valves to the cylinders.
So the piston slides in the cylinder, and these pistons connect to the jaws to get open and close.
These chucks are suitable for only ferrous metals. This type of chuck is suitable for those metals which can not sustain pressure applied by the jaws of another type of chucks. In most cases, an electromagnet is there to make a magnetic force to clamp the workpiece.
When we switch ON the power, flux develops in it to create magnetic force. During the removal of the workpiece, we can switch OFF the power. By using ‘keepers’ we can short the circuit and prevent the flux from passing through the workpiece.
It is suitable for holding long parts. These parts pass through the spindle and are clamped in the collet attached to the front end of the spindle. The shape of the collect is round, hexagonal, etc depending on the type of workpiece.
Collet has an external thread lengthwise. During the fixing of collect into the spindle, a key is inserted in the hole of the chuck to engage the thread with the collet to get better fixing. By loosening the key, we can disengage the collet.
It is a combination of four jaw chuck and universal chuck. We can move their jaws independently, or with some adjustment, we can move their jaws simultaneously.
Drill Chuck– It uses for holding shank drills or tap for respective operations.
Tailstock fixes on the right-hand side of the lathe bed. It gives support to the workpiece during the machining operation, and it holds a tool during drilling, tapping, reaming, etc. According to the length of the workpiece, we can slide tailstock on the guideways and adjust at a specific distance.
In the barrel of the tailstock casting, the spindle is there to hole drilling, tapping, reaming, etc tools. The spindle can move outside or inside with the help of a hand wheel having a square threaded screw connected to the spindle. To engage square threaded screw with the spindle the bush is at the backside of the spindle with the same threads for giving good engagement. The front end of the spindle is in taper in cross-section for better fixing of the tool in it.
By rotating a handwheel in a clockwise, and anticlockwise direction, we can move the spindle with the tool in the forth and back direction. With a spindle clamp, we can clamp the spindle at the desired length. To clamp a tailstock at a specific position, we can use a locking lever.
To remove the tool from the tailstock, we can rotate the handwheel to its extreme back position to touch the wheel screw to the backside of the tool to apply pressure.
A carriage is a combination of the parts to guide, move, support, and control the motion of the cutting tool. It consists of the following parts.
The saddle is an H shape casting that fits the bed and slides along with the guideways. Cross slide and tool post is the part of the saddle.
8. Cross Slide
It is a machined dovetail shape part that fits into the saddle to achieve cross-movement at a right angle to the lathe axis. With the handwheel of the cross slide, we can move the cross slide.
9. Compound rest
Compound rest mount on the cross slide, which has a circular dial of angle. Its function is to arrange compound rest at a specific degree to achieve cuts in angular and tapers. With the compound rest handle, we can give motion. It is a manual operation to do. Compound rest handle having micrometer guide to decide the depth of cut.
Toolpost fix on the top of the compound rest to hold and adjust the tool. We can clamp the tool like the single-point cutting tool, knurling tool, etc to do the operation.
Apron contains gears, levers, clutches, etc for the operation of carriage. It plays a main role in automatic feeds. By engaging the split nut with the lead screw, we can carry internal or external threads. Handwheel of the apron help to move the carriage forth and back direction.
It is a power source of the lathe machine. When the motor turns ON it transfers the rotating motion through a belt drive, chain drive, or gear drive to the spindle of the headstock. Due to that chuck rotate at a specific speed.
13. Lead Screw
The lead screw is the square threaded long shaft. It only comes in operation during thread cutting. It gives automatic linear motion during thread cutting operation. During an ideal condition, it gives the motion during boring and turning operation.
14. Feed Rod
The feed rod helps to transfer motion from the lathe spindle to the apron assembly by the feed rod. There are in between so many gear arrangements are there to transfer motion. Feed rods help during turning, facing, and all other operations on the lathe machine by giving motion to the carriage.
15. Thread cutting mechanism
This mechanism operates by the half nut mechanism. This mechanism engages or disengages carriage with the lead screw. The closing of the half nut allows the carriage to move at a fixed distance.
Split nut using only during thread cutting, not for other operations.
16. Chip Pan
It is for collecting chips formations during the various operations on the lathe machine. It is at bottom of the lathe machine.
It is present inside of the headstock. It gives variation in speed with a geometric ratio as per requirement by moving a lever.
18. Cooling Devices
During the operations on the lathe machine, a cooling agent is necessary to reduce heat formation. So cooling water pump sprays the cooling medium during operation to reduce heat and remove chips from the working area into the chip pan.
On the leg, the whole mass of the machine is balanced. These legs are bolted to the foundation with bolts to transfer machine vibrations to the ground. It is necessary to pass a certain amount of machine vibrations to earth for better stability.