The Lathe

                                           The Lathe

The primary purpose of the lathe is to machine cylindrical forms. The

contour is generated by rotating the work with respect to a single-point

cutting tool. For machining the outside

surface, the cutter is moved

parallel to the axis of rotation. This operation is called turning.

Alternatively, the metal may be removed from the inside of the work in which

case the operation is called boring. When the tool is moved across the face

of the work it is called facing.

The principal parts of the lathe are illustrated  The

workpiece is secured at one end in a chuck and supported at the other end

by a center, fitted in the tailstock. The chuck is mounted on the headstock

spindle and driven by an electric motor via a gearbox and transmission

system (the last two items are not shown). The headstock and tailstock are

both attached to the machine bed, and the position of the tailstock is

adjustable to accommodate various lengths of the workpiece.

CROSS-SLIDE

Lathe

The cutting action is by means of a single-point cutting tool mounted in

a tool holder. The cutting tool is positioned, prior to the commencement of

the cutting operation, so that the cutting point is in line with the axis of

the work. The tool can be moved, primarily, in two directions. For normal

turning and boring, a longitudinal movement is required and this is

achieved by moving the carriage along the slideways of the bed. For facing

the end of the work-piece, a transverse movement is required and this is

achieved by moving a cross-slide along the slideways of the carriage. Note

that these slideways are at right angles to the bed slideways. Both the

longitudinal and transverse movements can be power operated.

The speed of the carriage (or cross-slide) relative to the rotational

speed of the work is adjustable and this, together with the depth of cut

chosen, determines the finish obtained on the work. For rough machining,

a relatively deep cut with a fast feed is used, but for finishing a shallow cut

with a fine feed is required. When a large amount of metal has to be

removed, a number of successive roughing cuts are made until the

required diameter is approached. The part is then finished to size with one

or two finishing cuts.

The lathe is extremely versatile and is used for making a large variety of

mould parts. For example, guide pillars, guide bushes, circular support

blocks, ejector rods, ejector rod bushes, push-back pins, etc., are all

manufactured on the lathe. In addition to this bolster work, the cavity and

core are also produced on a lathe if the moulding form is cylindrical.