Manufacturing Process - Lath Machine

v Lathe is a machine that removes metal from work piece by spinning a block of material to perform various operations such as:
o   Cutting off
o   Straight turning.
o   Grooving.
o   Facing.
o   Taper Turning
o   knurling
o   Drilling.
o   Threading.

v Components of lathe machine:
1.      Bed.
2.      Carriage.
3.      Headstock.
4.      Tailstock.
5.   Feed rod

Fig(1) lathe components
1. Bed:
·         The structure that supports all the components of the lathe machine.
·         Made of strong material with high wear resistance and high dimensional accuracy.
2. Carriage:
·         Carriage holds the tool and moves it longitudinally (turning) or perpendicularly (facing) under the control of the operator.
3. Head Stock.
·         The part that contains the spindle and the chuck which holds the WP
4.  Tail Stock
·         Tail stock is  a tool (drill), and center mount, opposite the headstock which slides longitudinally and help support the work piece(WP).
·         The center could be fixed or could rotate freely with the WP


v Lathe Specifications
A lathe is generally specified by;
·         Its swing, the maximum diameter of the workpiece that can be machined.
·         The maximum distance between the headstock and tailstock centres.
·         The length of the bed.

v Types of lathe machines:

  1. Bench lathe: a small size lathe with low power used to turn small pieces.
                                  Fig (2) Bench lathe

  1. Engine lathe: the most common lathe, come with a variety of size, power and shapes.


                              Fig(3) Engine lathe

  1. Tracer lathe: a lathe that is capable of turning parts with various contours.

                                          Fig(4) Tracer lathe

4.      Automatic Lathe: a lathe that works automatically without the requirement of an
operator.


                                              Fig(5) Automatic lathe

  1. Turret lathe:  a multi purpose lathe which have multiple tools fixed on its carriage or
    its tailstock.


                                               fig (6) Turret lathe
  1. Computer Controlled Lathe: a highly automated lathe with high precision and usually
    controlled using Codes

                                                Fig (7) Computer Controlled lathe

v Lathes are selected according to
—  Engine Power, Kw
—  Max length between tailstock and headstock.
—  Maximum speed, rpm.


v Work Piece fixture  to the Lathe:
There is the most common way for fix the workpiece to the lathe:

o   Independent Chuck - (4 Jaw)
The independent chuck has four jaws which are adjusted individually on the chuck
Face by means of adjusting screws. The chuck face is scribed with concentric circles which are used for rough alignment of the jaws when chucking round workpieces. The final adjustment is made by turning the workpiece slowly and using dial indicators to determine its
Concentricity and to the desired tolerances. The jaws of the independent chuck may be used as in the figure shown, or may be reversed so that the steps face in the opposite direction; thus, Workpieces can be gripped either externally or internally. The independent chuck can he used to hold square, round, octagonal, or irregular shaped workpieces in either a concentric or eccentric position due to the independent operation of each jaw. Because of its versatility and capacity for fine adjustment, the independent chuck is commonly used for mounting
workpieces that require extreme accuracy.


Fig (8) Independent Chuck - (4 Jaw)


o   Universal Scroll Chuck - (3 Jaw):

The universal scroll chuck has three jaws which move in unison as an adjusting pinion is rotated. The advantage of the universal scroll chuck is its ease of operation in centering the work for concentric turning. This chuck is not as accurate as the independent chuck but, when in good condition, it will center the work automatically within 0.003 of an inch of complete accuracy.
The jaws are moved simultaneously within the chuck by means of a scroll or spiral threaded plate. The jaws are threaded to the plate and move an equal distance inward or outward as the scroll is rotated by means of the adjusting pinion. Since the jaws are individually aligned on the scroll, the jaws cannot be reversed. However, the chuck is usually supplied with two sets of jaws which can be interchanged.
The universal scroll chuck can be used to hold and automatically center round or hexagonal work pieces. Having only three jaws, the chuck cannot be used effectively to hold square, octagonal, or irregular shapes



Fig (9) Universal Scroll Chuck - (3 Jaw)

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