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Introduction and Difference Between Jig And Fixture

Introduction and Difference Between Jig And Fixture

 Definition Of Fixture And Jig 

Fixtures, being used in machine shop, are strong and rigid mechanical devices which enable easy, quick and consistently accurate locating, supporting and clamping, blanks against cutting tool(s) and result faster and accurate machining with consistent quality, functional ability and interchangeability.

Jig is a fixture with an additional feature of tool guidance.

Introduction To Jig and Fixture:

The jigs and fixtures are the economical ways to produce a component in mass. So jigs and fixtures are used and serve as one of the most important facility of mass production system. These are special work holding and tool guiding device. Quality of the performance of a process largely influenced by the quality of jigs and fixtures used for this purpose. What makes a fixture unique is that each one is built to fit a particular part or shape. The main purpose of a fixture is to locate and in the cases hold a workpiece during an operation. A jig differs from a fixture in the sense that it guides the tool to its
correct position or towards its correct movement during an operation in addition to locating and supporting the workpiece.

An example of jig is when a key is duplicated, the original key is used as base for the path reader which guides the movement of tool to make its duplicate key. The path reader of a CWC machine here works as a jig and the original is called template. Sometimes the template and jig both are the name of same part of a manufacturing system.

JIGS
Jigs along with fixtures are specifically designated machine parts, which can be manufactured by any of the following methods : 
(a) Machining, (b) Forging, (c) Casting and (d) Complicated.

Jigs are fabricated in different pieces and joined together by welding.
Normally jigs are made of hardened steel, which are wear resistant, corrosion resistant, and thermally in sensitive. Their dimensional accuracy directly influences the accuracy of performance of the operations where these are used.


FIXTURES

Fixtures are designed specifically for an operation and so these are named on the base of the operation to be carried out with their help. Fixtures are used to hold the workpiece properly to carryout the operations. Different types of fixtures are listed below.
(a) Turning fixtures
(b) Milling fixtures
(c) Fixture for grinding
(d) Fixture for broaching
(e) Fixture for boring/drilling
(f) Tapping fixture
(g) Fixture for welding
(h) Assembling fixture
Fixture Example which hold complex Pipe
Image Courtesy                                                              Fixture Example which hold complex Pipe

PURPOSE AND ADVANTAGES OF JIGS AND FIXTURES 

Following the purpose and advantages of jigs and fixtures :

(a) It reduces or sometimes eliminates the efforts of marking, measuring and setting of workpiece on a machine and maintains the accuracy of performance.

(b) The workpiece and tool are relatively located at their exact positions before the operation automatically within negligible time. So it reduces product cycle time.

(c) Variability of dimension in mass production is very low so manufacturing processes supported by use of jigs and fixtures maintain a consistent quality.

(d) Due to low variability in dimension assembly operation becomes easy, low rejection due to les defective production is observed.

(e) It reduces the production cycle time so increases production capacity. Simultaneously working by more than one tool on the same workpiece is possible.

(f) The operating conditions like speed, feed rate and depth of cut can be set to higher values due to rigidity of clamping of workpiece by jigs and fixtures.

(g) Operators working becomes comfortable as his efforts in setting the workpiece can be eliminated.

(h) Semi-skilled operators can be assigned the work so it saves the cost of manpower also.

(i) There is no need to examine the quality of produce provided that quality of employed jigs and fixtures is ensured.

Difference Between Jig And Fixture in Tabular Table:

Jig
Fixture
1. It is a work holding device that holds, supports and locates the workpiece and guides the cutting tool for a specific operation
1. It is a work holding device that holds, supports and locates the workpiece for a specific operation but does not guide the cutting tool
2. Jigs are not clamped to the drill press table unless large diameters to be drilled and there is a necessity to move the jig to bring one each bush directly under the drill.
2. Fixtures should be securely clamped to the table of the machine upon which the work is done.
3. The jigs are special tools particularly in drilling, reaming, tapping and boring operation.
3. Fixtures are specific tools used particularly in milling machine, shapers and slotting machine.
4. Gauge blocks are not necessary.
4. Gauge blocks may be provided for effective handling.
5. Lighter in construction.
5. Heavier in construction.

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