Table of Contents

Main Parts of Capstan Lathe and Turret Lathe

Capstan and Turret lathes

Turret and capstan lathes are the natural development of the engine lathe, where the tailstock is replaced by an indexable multistation tool head, called the capstan or the turret. This head carries a selection of standard tool holders and special attachments. A square turret is mounted on the cross slide in place of the usual compound rest in engine lathe. Sometimes a fixed tool holder is also mounted on the back end of the cross slide. Dimensional control is effected utilizing longitudinal (for lengths) and traversal (for diameters) adjustable stops.

Capstan and Turret lathes are production lathes use for assembling of a huge number of comparable workings in the slightest feasible time. These lathes are progression above center lathes. Machining of a job on a center lathe takes extensive time, which is avoided on a turret lathe with the assimilation of services for moving eight or extra tools. Characteristic features of these machines are capstan or turret head mount on the bed. Tool can attach to every face of turret head. On capstan lathe drive to the turret is given as of a support slide clamped to the top of the bed. Turret is changeable so that its distance as of machine nose can be diverse. Turret of turret lathe is mounting on saddle slides straight on a bed in a similar way as a lathe saddle. It is the difference of form of carrying turret which distinguishes capstan lathe as of turret lathe. In all other respect these machines are comparable.

The semiautomatic lathes, capstan lathe, and turret lathe are very similar in construction, operation, and application. schematically shows the basic configuration of capstan lathe and Fig. shows that of turret lathe.

In contrast to center lathes, capstan, and turret lathes

• are semiautomatic

• possess an axially movable indexable turret (mostly hexagonal) in place of tailstock

• holds a large number of cutting tools; up to four in indexable tool post on the front slide, one in the rear slide and up to six in the turret (if hexagonal) as indicated in the schematic diagrams.

• are more productive for quick engagement and overlapped functioning of the tools in addition to faster mounting and feeding of the job and rapid speed change.

• enable repetitive production of the same job requiring less involvement, effort and attention of the operator for pre-setting of work–speed and feed rate and length of travel of the cutting tools

• are relatively costlier

• are suitable and economically viable for batch production or small lot production.

Difference Between Capstan and Turret Lathe :

The essential components and operating principles of capstan and turret lathes are illustrated schematically in Figure Capstan lathes are mainly used for bar work, whereas turret lathes are applicable for large work in the form of castings and forgings.
In a capstan or ram-type lathe, the hexagon turret is mounted on a slide that moves longitudinally in a stationary saddle (Figure a). During the setup of the machine, the saddle is positioned along the bed to give the shortest possible stroke for the job. The advantage of the capstan lathe is that the operator has less mass to move, resulting in easier and faster handling. The disadvantage is that the hexagonal turret slide is fed forward such that the overhang is increased, resulting in the deflection of the ram slide, especially at the extreme of its position, which produces taper and reduces accuracy.

In the turret- or saddle-type lathe, the turret is mounted directly upon a movable saddle, furnished with both hand and power longitudinal feed (Figure b). This machine is designed for machining chuck work, in addition to bar work. Owing to the volume of the swarf produced, the guideways of the machine bed are flame-hardened and provided with covers that protect the sliding surfaces. The bed must be designed to allow free and rapid escape of swarf and coolant.

Turret Lathe type :

A turret lathe is a manual lathe having a hexagonal tool-holding turret in place of the tailstock of an engine lathe. The headstock in most cases is geared with provision for 6 to 16 spindle speeds and may double this capability with a twospeed motor. Some turret lathes are designed and equipped for working on barstock and are called bar-type machines. The name screw machine or hand screw machine has been used for such machines, particularly in the smaller sizes. Other turret lathes are equipped for chuck work.

Horizontal Turret Lathes –

The name turret lathe alone ordinarily implies a horizontal spindle machine. This type of lathe is made in two general designs, known as ram and saddle.

Ram-type turret Lathe –

A ram-type turret lathe carries the turret on a ram . The ram slides longitudinally on a saddle positioned and clamped on the ways of the bed. Tools in their holders are mounted on the faces of the turret, and the tools on the face.toward the headstock are fed to the work when the ram is moved to the left. When the ram is withdrawn, the turret indexes, and the next face, called a station, is positioned to face the headstock.

A ram is lighter and can be moved more quickly than a saddle, but lacks some rigidity. Because of convenience and speed, the ram-type construction is favored for small- and medium-size turret lathes for which the ram does not have to overhang excessively.

Saddle-Type.

The hexagonal turret of a saddle-type turret lathe is carried directly on a saddle that slides lengthwise on the bed (Fig.). This construction is favored for large turret lathes because it provides good support for the tools and the means to move the tools a long distance when necessary.
The saddle is moved toward the headstock by hand or power to feed the tools to the work and is withdrawn to index the turret. The turret is fixed in the center of the saddle on some machines. On others it may be moved crosswise. This helps reduce tool overhang for machining large diameters and is helpful for taper or contour boring and turning.
Most saddle-type turret lathes have a side hung carriage that does not extend across the entire top of the bed and allows larger pieces to be swung. As a result, the rear tool station on the cross slide is lost.

Vertical Turret Lathes.

With these lathes, the work is mounted on a rotating table, and the tools are mounted on vertical rams or turrets. Vertical turret lathes are used primarily for short, heavy, large-diameter workpieces. They are also ideal for light-weight but bulky parts. Controls are usually automatic (plugboard or cam) but can also be manual or numerical control.

1. Bed –

The bed is a long box-like casting with accurate guideways on which carriage and turret saddle are mounted. The bed is designed to ensure strength, rigidity, and permanency of alignment under heavy-duty services. Carriage is mounted over the bed and travels longitudinally.

2. Headstock –

Headstock is a large casting located at the left-hand end of the machine. The headstock of a capstan and turret lathe may be of following types:

(i) Step Cone Pulley Driven Headstock –

This is the simplest type of the headstock and is fitted with small capstan lathes where the lathe is engaged in machining small and almost constant diameter of workpieces. Only three or four steps of the pulley can cater to the needs of the machine. The machine requires special counter shaft unlike that of an engine lathe, where starting, stopping, and reversing of the machine spindle can be affected by simply presenting a foot pedal.

(ii) Electric Motor Driven Headstock –

In this type of headstock the spindle of the machine and the armature shaft of the motor are the same. Any speed variation and reversal is affected by simply controlling the motor. Three or four speeds are available and the machine is suitable for a smaller diameter of workpieces rotated at high speed.

(iii) All Geared Headstock –

On the larger lathes, the headstock is geared and different mechanisms are employed for speed changing by actuating levers. The speed changing may be affected without stopping the machine.

3.Turret Saddle –

This saddle replaces the tailstock of a center lathe. It is mounted directly on the lathe bed on the same side as a tailstock in the center lathe. It can be of two types one is that which travels longitudinally along with the tool when it is fed into the job and the turret head carrying the tool is mounted directly on it. In the other type, it is provided with a slide that moves in the guideways made in it. In this type the turret head is mounted on the slide. As the overhang of the slide is kept limited, the saddle can be moved along the bed and secured at the desired position. During the operation it remains stationary and the tools are fed longitudinally by moving the slide. The former type of saddle is provided on the saddle type turret lathes and the latter type on the ram type turret lathes or capstan lathes.

4. Cross Slide and Saddle.

In small capstan lathes, hand-operated cross slide and saddle are used which are clamped on the lathe bed at the required position.

5.Tool accessories

The different tools and accessories use in a center lathe, some tools are used for manufacture work on a turret lathe:

1. Tap with die holder

2. Adjustable Shaft tool holder

3. Boring heads

4. Rear tool holder

5. Straight Shaft tool holder

6. Multi-tool holder

7. Split bushes

8. Long with short tool holders