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Different parts of lathe machine and their functions

We were discussing the types of lathe machines and their use in our previous post. Now we will see here the different parts of the lathe machine and their functions with the help of this post. 

Center lathe

The principal parts of a center lathe are labeled and displayed here in the following figure.  A brief description of these parts are described as follows. 

Figure : Center Lathe Machine 


The lathe bed forms the base of the machine. It is made of cast-iron or alloy steel. It consists of flat or inverted V-shaped inner and outer guideways to guide the carriage, headstock and tailstock. 

The height of the lathe bed should be appropriate to enable the technician to do his job easily and comfortably. Many lathes are made with a gap in the bed. This gap is used to swing extra large diameter pieces. 


The headstock is fixed at the left-hand side of the lathe bed on the inner guideways. It supports the spindle. The spindle is driven through the gearbox which is housed within the headstock. 

The function of the gearbox is to provide a number of speeds to the spindle. The spindle is always hollow to feed the barstock through that hole for continuous production. The nose of the spindle is threaded to mount the chuck or face plate. 


The tailstock is displayed here in the following figure. It is located on the inner guideways at the right-hand side of the operator. The main purpose of the tailstock is to support the free end of the workpiece when it is machined between centers. It is also used to hold tools for operations such as drilling, reaming, tapping, etc. 

To accommodate different lengths of work, the body of the tailstock can be adjusted along the guideways by sliding it to the required position and can be clamped by the bolt and plate. The body is bored to act as a barrel which carries a quill that moves in and out of the barrel. The movement of the quill is achieved by means of a hand wheel and a screw which are engaged with a nut fixed in the quill. The hole in the open side of the quill is tapered to mount lathe centers or other tools like twist drills or boring bars. 

The upper body of the tailstock can be moved towards or away from the operator by means of the adjustment screws to offset the tailstock for taper turning. 

Figure : Tailstock 


The lathe carriage is displayed here in the following figure. It has several parts that support, move and control the cutting tool. It consists of the following parts as mentioned below. 

  1. Saddle 

  2. Cross-slide 

  3. Compound rest 

  4. Tool post 

  5. Apron

Figure : Lathe Carriage 


The saddle is an H-shaped casting that fits over the bed and slides along the guideways. It carries the cross-slide and tool post. 


The cross-slide carries the compound rest and tool post. It is used to give depth to a cut.

Compound rest  

It has a circular base with graduations and is mounted on the cross-slide. It is used for turning short tapers and angular cuts.

Tool post  

This is located on the top of the compound rest to hold the tool and to enable it to be adjusted to a convenient working position. The various types of tool posts used in a lathe are displayed here in the following figure. 

Figure : Tool Posts used in turning 

Single screw tool post 

This consists of a round bar with a slotted hole in the center for fixing the tool by means of a set screw. The tool post with a concave ring and convex rocker slides in a T-slot on the top of the compound rest. The height of the tool point can be adjusted by tilting the rocker and clamping in position by means of a set screw.

Four-way tool post  

In this type of tool post, four sides are open to accommodate four tools at a time. 

Quick change tool post 

Modern lathes are provided with this type of tool posts. Instead of changing the tools, the tool holder is changed in which the tool is fixed. This is expensive and requires a number of tool holders. But it has the advantage of ease of setting the center height and rigidity of the tool. 


The apron is fastened to the saddle and hangs over the front of the bed. It contains gears, clutches for transmitting motion from feed rod to the carriage and also contains a split nut which engages with a lead screw while thread-cutting. 

Lead screw 

The lead screw is a long screw with ACME threads. It is used for transmitting power for automatic feed or feed for thread cutting operation. 

We will see how a lathe can be completely specified. We will basically study the complete specifications of lathe in our next post. 


Engineering Practices By Mr. S. Suyambazhahan

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