Lathe machine and its components and working

About lathe machine and its parts and working for mechanical engineers

1. A lathe machine is a machine tool which removes the undesired material from a rotating workpiece in the form of chips with the help of a tool which is traversed across the work and can be feed deep into the work . A lathe is a machine which is one of the most versatile and widely used machine tool all over the world. Lathe is also known as the ‘Mother of all Machines’. Lathe Machine has become a general-purpose machine tool, employed in production and repair work, because it permits a large variety of operations to be performed on it. Center lathe

2. Figure 1: Image of typical lathe machine with their parts.

3. Limitation of Center lathe Setting time for holding job is very high. Only one tool can be used generally at a time. Idle time in between the operation is high. Preciseness of the job depends highly on the skills of operator. For overcoming limitations of Centre lathe, Capstan, Turret and Automatic lathe are invented. They have basically achieved improvements in the following areas: Work holding methods. Multiple tool availability. Automatic feeding of tool. Automatic stopping of tool at precise locations. Automatic control of proper sequence of operations.

4. Capstan and Turret lathe The capstan and turret lathe consists of a bed, all geared headstock, and a saddle on which a four station tool post is mounted to hold four different tools. A tool post fitted at the rear of the carriage holds a parting tool in an inverted position. The tool post mounted on the cross-slide is indexed by hand. A capstan and turret lathe is a semi- automated production lathe. It is used to manufacture any number of identical pieces in the minimum time. A turret lathe, a number of tools can be set up on the machine and then quickly be brought successively into working position so that a complete part can be machined without the necessity for further adjusting, changing tools, or making measurements. The same case is with Capstan lathe.

5. The capstan lathe carries the hexagonal turret on a ram or a short slide. The ram slides longitudinally on a saddle positioned and clamped on lathe bed ways. This type of machine is lighter in construction and is suitable, for machining bar of smaller diameter. The tools are mounted on the square turret and six faces of the hexagonal turret. The feeding movement is obtained when the ram moves from left to the right, and when the ram is moved backward the turret indexes automatically and the tools mounted on the next face comes into operation. In the case of turret lathe, the turret is mounted on the saddle which slides directly on the lathe bed ways. This type of construction provides utmost rigidity to the tool support as the entire cutting load is taken up by the lathe bed directly. In the case of a capstan lathe as the ram feeds into the work, the overhanging of the ram from the stationary saddle presents a non-rigid construction which is subjected to bending, deflection or vibration under heavy cutting load.

6. Different parts of Capstan lathe are: Head stock Cross-slide tool post Hexagonal turret Saddle for auxiliary slide Auxiliary slide Feed rod Saddle for cross-slide. Different parts of turret lathe are: Head stock Cross-slide tool post Hexagonal turret Turret saddle Feed rod Saddle for cross-slide.

7. Pictorial view of Capstan and Turret lathe, respectively.

8. Capstan lathe Turret lathe Short slide, since the saddle is clamped on the bed in position. Saddle moves along the bed, thus allowing the turret to be of large size. Light duty machine, generally for components whose diameter is less than 50 mm. Heavy duty machine, generally for components with large diameters, such as 200 mm. Too much overhang of the turret when it is nearing cut. Since the turret slides on the bed, there is no such difference. Ram-type turret lathe, the ram and the turret are moved up to the cutting position by means of the capstan Wheel. As the ram is moved toward the headstock, the turret is automatically locked into position. Saddle-type lathes, the main turret is mounted directly on the saddle, and the entire saddle and turret assembly reciprocates.

9. Turret indexing mechanism The hexagonal turret is rotated (for indexing) by a Geneva mechanism where a Geneva disc having six radial slots is driven by a revolving pin. Before starting rotation, the locking pin is withdrawn by a cam lever mechanism. The single rotation of the disc holding the indexing pin is derived from the auxiliary shaft with the help of another single revolution clutch as indicated. For automatic lathe: Ratchet and Pawl mechanism