Jigs And Fixtures

INTRODUCTION

A jig is a special device which holds and supports the work piece to be machined and guide the cutting tool as the operation is performed. It is amass production tool because in mass production quantities of components to be produced are too large, so a faster and more profitable device is required to position the work piece in the correct relationship to the cutting tool and quickly clamped before machining takes place. Such a device is known as Jig.

A jig is often confused with a fixture; a fixture holds the work piece in a fixed location. A device that does both functions (holding the work piece and guiding the toll) is called Jig.

In short, the device which locates and holds the work piece in the positive manner and also guides the cutting tool such that it is in the correct relationship to the work piece to be performed is known as Jig.

Function Of Jig

Some important functions of jig by which it becomes the most important device of production process are given bellow:-

It holds and locates the work piece to be machined.

It guides the cutting tool while performing the operation.

It controls the motion of other tools.

It provides repeat ability, accuracy and interchangeability in the manufacturing of products.

Difference Between Jig & Fixture

If you work in machining environment, then you have probably heard the terms "Jig" and " Fixture". You probably also know that both jigs and fixtures have something to do with holding work pieces for machining operations. But the real distinctions between them are given in table.

S.No.	Jig	Fixture
1.	It holds and locates the work piece and guides the cutting tool.	It holds and locates the work piece with reference the cutting tool.
2.	It is lighter in construction.	It is heavier in construction.
3.	This device is used in drilling, reaming, tapping chauffeuring, countersinking operations.	This device is used in milling, grinding and turning operations.

Types Of Jig

The most common jigs are boring and drilling. These tools are fundamentally same. The difference lines in the size, type and placement of the drill bushing.

• Boring Jig : The jigs which are used to bore holes that either are too large to drill or must be made an odd size is called Boring Jig. They usually have larger bushing. These usually may also have internal oil grooved to keep the boring bar lubrication. Often, boring jigs have more then one bushing to support the boring bar throughout the machining cycle.

• Drilling Jig : A device which is used to hold, locate the work piece and guide the cutting tool during operations known as Drilling Jig. It is the most widely used from of jig. They are used for drilling, reaming, tapping, chauffeuring, counter boring, countersinking, and similar operations. The shape and size of the drilling jig varies jig varies with the shape and arrangement of their parts.

Parts Of Drilling Jig : Some important parts of drilling jig are given below :-

1. Base : Base is the most important part of drilling jig. It is that part upon which all other parts are supported. It secures the operating parts of the machine tool.

2. Clamping Device : As the name indicates, the device which is used to clamp the work piece in different positions with relation to the drilling tool is known as clamping device.

3. Locator : The device which is used to located the job for correct location of the drilling tool is knows as locator.

4. Body : Body is that part of drilling jig which supports bushes to guide the drilling tool.

5. Bushes : The part which guides the drilling tool is known as bushes.