14 February 2017

Capstan and turret lathe

Introduction :
A capstan and turret lathe is a production lathe. It is used to manufacture any number of identical pieces in the minimum time.
These lathes were first developed in the United States of America by Pratt and Whitney in 1960.

Types of the machine :
There are two main types of horizontal lathe of this family are :

  • The capstan or Ram type lathe
  • The turret or Saddle type lathe
The capstan or Ram type lathe :

Capstan lathe

The ram-type lathe carries the hexagonal turret on a ram or a short slide.
The ram slides longitudinally on a saddle and clamp-on lathe bed ways.
This type of machine is lighter in construction and it is suitable for machining bar of smaller diameter. The tools are mounted on the square turret and six faces of the hexagonal turret.
Ram moves from left to right the feeding movement is obtained.

The turret or Saddle type lathe :

Turret lathe

The hexagonal turret-mounted directly on a saddle and the whole unit moves back and forth on the bed ways to apply feed.
This type of turret lathe is heavier in construction and is particularly used for larger diameter bar work and chucking.work.

Principle parts of Capstan and Turret lathe :

Bed :
The bed is long box-like casting provided with accurate guide ways upon which are mounted the carriage and turret saddle.
The bed is designed to ensure strength, rigidity and permanency under heavy duty services.

Head stock :
The head stock is a large casting located at the left hand of the bed.
Different types of head stock maybe use that are listed below :

  • Step cone pulley driven head stock
  • The direct electric motor is driven head stock
  • All geared head stock
  • Perspective head stock
Cross-slide & Saddle :
In small capstan and turret lathe hand-operated cross-slide and saddle are used which are clamped on the lathe bed at the required position.
The larger capstan lathes are usually used two designs of the carriage like :
  • Conventional type carriage
  • Side hung type carriage 
The turret saddle and auxiliary slide :
The turret saddle bridges the gap between two-bed ways and the top face is accurately machined to provide a bearing surface for the auxiliary slide.
The hexagonal turret is mounted on the auxiliary slide.

Capstan and turret lathe mechanism :
The carriage, cross-slide and turret slide may be fed into the work by hand or power. 
The various mechanism for machining. 
  • Turret indexing mechanism
  • Bar-feeding mechanism
Capstan and turret lathe operation :
In this lathe operations are similar to that of the centre lathe machine.
The usual operations performed in this lathe are :
  • Straight turning
  • Shoulder turning
  • Taper turning
  • Chamfering
  • Thread cutting
  • Facing
  • Knurling
  • Forming
  • Drilling
  • Reaming
  • Boring
  • Counter boring
  • Tapping
  • Undercutting
  • Parting off 
Cutting speed, feed and depth of cut are similar to the simple lathe machine.