Page 81 - CITS - Fitter Trade Practical - Volume -2

FITTER - CITS

Drilling jig types and uses

Objectives : At the end of this exercise you shall be able to
• what is jig
• list the different types of drill jig and their uses.

Introduction to jigs

A jig is a device in which a work piece/component is held and located for a specific operation in such a way that
it will guide one or more cutting tools to the same zone of machining.
Types of drill jigs

Drill jigs may be divided into two types
- Open
- Closed
Open jigs are used when the operation is to be done only on one side of the piece. Closed jigs (Box jig) are used
when the operations are to be done on more than one side of the piece. Jigs are identified according to the way
they are built. Most commonly used jigs are:

- Template jig
- Plate jig
- Table jig
- Sandwich jig

- Angle plate jig
- Modified angle plate jig
- Box jig
- Channel jig
- Leaf jig

- Indexing jig
- Solid jig
- Post jig
- Trunnion jig

Types of drill jigs
Template jigs
This type of jigs fits over on or into the work and is not usually clamped. They are simple and cheap. They may or
may not have guide bushes. When bushes are not used the whole jig plate may be (Fig 1)
The design of a particular type of jig will be based on:
- the position wherein the drilling or its allied operation / operations are to be performed
- the shape of the piece part.

Plate jig
This jig consists of a drill plate which rests on the component to be drilled. For correct positioning/locating, pins
and clips are provided. For heavier piece parts, sometimes clamps are not used. Generally a base plate will not
be available for this type of jigs. (Figs 1, 2 and 3)
Table jig (Turnover jig)
This is used when it is necessary to locate the piece part from its face. For accurate seating of the jig on the
machine table, four legs will be provided on this type of jig. (Fig 4)

66

CITS : C G & M - Fitter - Exercise 66