Main Parts of Capstan and Turret Lathe

Turret lathe has essentially the same parts as the engine lathe except the turret and the complex mechanism incorporated in it for making it suitable for mass production. Figure below illustrates the different parts of a capstan and turret lathe. The following are the principle part of a capstan and turret lathe:
Capstan Lathe
Turret Lathe
(a) Bed - The bed is a long box like casting with accurate guide ways 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.

(b) 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 work pieces. Only three or four steps of 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 one and 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 smaller diameter of work pieces rotated at high speed.

(iii) All Geared Headstock - On the larger lathes the headstock are geared and different mechanism are employed for speed changing by actuating levers. The speed changing may be affected without stopping the machine.

(iv) Pre-optive or Pre-selective - It is an all geared headstock with provisions for rapid stopping, starting and speed changing for different operations by simply pushing a button or pulling a lever. For different operations and for turning different diameters, the speed of spindle must change. The required speed for next operation is selected before hand and the speed-changing lever is placed at the selected position. After the first operation is completed a button or lever is simply actuated and the spindle starts rotating at the selected speed required for second operation without stopping the machine. This mechanism is affected by friction clutches.

(c) Cross Slide and Saddle. In small capstan lathes, hand operated cross slide and saddle are used which are clamped on the lathe bed at required position. The large capstan lathes and heavy-duty turret lathes equipped with usually two designs of carriage:

(i) Conventional Type Carriage - The conventional type carriage bridges the gap between the front and rear bed ways and is equipped with four station type tool post at the front and rear tool post at the back of cross slide.

(ii) Side Hung Type Carriage - The side hung type carriage is generally fitted with heavy-duty turret lathes where the saddle rides on the top and bottom guide ways on the front of the lathe bed. The design facilitates swinging of larger diameter of work pieces with being interfered by the cross slide. The saddle of cross slide may be fed longitudinally or crosswise by hand or power. The longitudinal movement of each tool may be regulated by using stop bars or shafts against the stock fitted on the bed or carriage. These stops are set so that each tool will feed in to the work to the desired length for the purpose of duplicating the job without checking the machining lengths for different operations each time. These stops first trip out the feed and then serve as a dead stop for small hand operated movements of tool to complete the cut. The stop bar are indexed by hand synchronize with the indexing of tools. The tools are mounted on the tool post and correct heights are adjusted by using rockers and packing pieces.

(d) Turret Saddle - This saddle replaces the tail stock of a centre lathe. It is mounted directly on the lathe bed on the same side as a tail stock in the centre 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 which moves in the guide ways made in it. In this type the turret head is mounted on the slide. As the overhung 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.

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