Jig and Fixture: Difference, Types, Benefits and Uses

Concept and Types of Jig and Fixture:

The elements of Jig are as follow:

The Jig is made up of the following parts.

1.  Jig body
2.  Locators and clamp.
3.  Jig plate
4.  Bushes
5.  Mechanism.

1. Jig body:

The body of the Jig has a plate, box or pot and channel shapes made by casting and fabrication. The size of body, material and method of construction based on Job complexity and the overall economy.

2. Locator and Clamps:

Locators- It is defined as the device so designed that each successive workpiece, when loaded and clamped, will occupy the same position in the work holding device. Its feature should be swarf traps and have clearance were necessary to clear the machining burrs.

Clamps-  The clamping is a device which holds the workpiece at its thick sections. It prevents the distortion of the workpiece due to clamping forces and is so positioned that they can be operated easily and safely by the operator and where they can most effectively prevent movement of the clamped workpiece.

3. Jig plate:

The main function of the jig plate is to hold the bushes into their proper positions. The thickness of the jig plate depends upon the size of the bush. Generally, the length of the bush is taken equal to tool diameter or double than that. The Jig plate is shown in fig.

4. Bushes:

Jig bush is guiding the tool.

5. Mechanism:

To carryout machining operation at a desired angle, indexing mechanism is used. The mechanism includes gears, Ratchet, splined wheel etc. as per their requirements.

Types of Jig and Fixture:

Types of Jig:

Following are the fourteen different types of jig:

1. Template jig
2. Plate jig
3. Table jig
4. Sandwich jig
5. Box Jig or tumble Jig
6. Channel jig
7. Leaf jig
8. Angle plate jig
9. Modified angle plate jig
10. Indexing Jig
11. Trunnion jig
12. Multi-station jig
13. Latch jig
14. Turn over jig

1. Template jig:

It is generally used for too accurate operations. Such Jigs gets fitted above the Job, hence clamping is not necessary. 

Template jig

2. Plate jig:

It is same as template Jig. But in this Jig clamp is used to hold the job.

3. Table jig:

This one type of plate Jig. By adding legs in the construction of plate jig the table jig can be constructed. Due to these legs, Jig remains higher than the table and large job can be accommodated in it. Therefore, it is used for large size component.

4. Sandwich jig:

It is also another type of plate jig in which additional backplate is placed. It is used and for thin and soft jobs. It can prevent the distortion of such job under the action of cutting force.

Sandwich jig

5. Box Jig or tumble Jig:

This type of jig held the component from all the four sides. Therefore, of all surfaces of the job become possible without changing the job position in the jig. Top View and side view Of box shown.

Box Jig or tumble Jig

6. Channel jig:

This is a simple type of box Jig in which the job is held from two sides and therefore

machining of one side become possible as shown.

7. Leaf jig:

This is also a type of box Jig. But one leaf is hinged in it to achieve easy loading and unloading or the job.

Leaf jig

8. Angle plate jig:

This jig is used for machining the job at 90* to its mounting locators.

Angle plate jig

9. Modified angle plate jig:

This is one type of angle plate jig in which machining can be done at an angle other than 90* to mounting locators, as shown in fig.

Modified angle plate jig

10. Indexing Jig:

As its name suggests, it is used for machining at certain angles accurately.

Indexing Jig

11. Trunnion jig:

This is a jig used for indexing large job. The job is placed in a box carrier and then it is loaded

on the trunnion.

Trunnion jig

12. Multi-station jig:

The construction of multi-station jig is shown in fig. In this jig when drilling of one part is in progress, reaming of other parts can be done and operation of the third part also become possible. The final station of this jig is meant for loading and unloading the job.

Multi-station jig

13. Latch jig:

This is one type of drilling Jig. which is shown in fig. Drill bush is fitted in the latch as shown in the fig. therefore latch works as a Jig plate. The latch is located by means of side A and Slot B. nut 'X' is used to clamp the latch and screw is used to clamp the workpiece.

Latch jig

14. Turn over jig:

This is also a special type of drill Jig. It is also called open jig. It is used for drilling components of irregular shapes. As shown in fig. This jig is mounted on four-foot nuts. The component is clamped from the bottom side by a quick action nut. 

The workpiece can be easily loaded and the problem of swarf clearance is not remaining. The main disadvantage of this jig is that the component cannot get support from the bottom where drilling is done at the time of drilling the hole.

Also Read: Bourdon tube pressure gauge

 Types of Fixture:

Following are the eight different types of fixture.

1. Plate fixture
2. Angle plate fixture
3. Indexing fixture
4. vice jaw fixture
5. Turning fixture
6. Boring fixture
7. Broaching fixture
8. Welding fixture

1. Plate fixture:

This is a simple type of fixture. It is used by fixing clamps and locators as required on the plate.

Plate fixture

2. Angle plate fixture:

This is also a type of plate fixture, in which the Job is machined at right angles to its locators. It is shown in fig. In this type as shown in fig. modified angle plate fixture can be constructed to facilitate the machining at an angle other than 90*.

 Angle plate fixture

3. Indexing fixture:

It is used for machining the job at the desired angle. An indexing fixture certain jobs which can be machined accurately by using this fixture.

 Indexing fixture

4. Vice jaw fixture:

It is used for machining of small jobs. In this fixture instead of standard jaws of vice. Jaws having a shape of the job are used as shown fig.

Vice jaw fixture

5. Turning fixture:

Equipment used in mass production on production lathe with a View to increase manufacturing efficiency and productivity are called ''turning Fixture." 

Turning fixture

List of different turning fixtures is as under.

l. General-purpose fixture.

Three jaw chuck, four jaw chuck, collets, mandrel etc.

2. Special purpose fixture.

Soft Jaw chuck, Rocking jaw chuck and magnetic chuck.

3. Back plate fixture

4. Face plate fixture,

Lathe fixtures can be divided into two types as under,

I. Standard fixture.

2. Special fixture.

The three Jaw chuck, four jaw chuck, collet, mandrel etc. are called standard fixtures. Three jaw chuck can be used to hold the symmetrical jobs like round, square and hexagonal. The four-jaw chuck can be used in addition to the above shapes for rough castings, and for eccentric turning work. Collect is selected for bar stock. While mandrel is used for the parts like gear blank, pulley etc. But certain castings, forgings which cannot be held easily in standard fixtures can be held in special lathe fixtures like faceplate, angle plate etc. The use of backplate is also popular.

6. Boring fixture:

Following standard fixtures are also used on the boring machine. 1. Chuck 2. Mandrel 3. Collet etc. The boring operation can be performed on a boring operation drill press, milling machine, Lathe, boring machine and a vertical or horizontal boring mill. Over & above standard fixtures following fixtures are also used in boring are divided into two parts.

1. Rotating fixture

2. Stationary fixture

Boring fixture

Working of boring fixture:

Fig shows a horizontal boring fixture. Its working is same as that of a Jig because the cutting tool is guided in this fixture. Such jobs are difficult to be loaded on a lathe machine, therefore, in reality, this fixture is more important. 

It is located by means of pins on the job with the help of already drilled holes in the Job. Strap clamp is used for clamping. Steadying screws are also used as the height of the Job is more. The light clamping is selected owing to the less cutting force in boring operation. 

Setting gauge is used for setting the boring bar, hence the accurate size of the hole can be produced. The fixture is arranged on the machine by using the tenons. To safeguard against the revolving tool, a speedily replaceable guard is provided.

7. Broaching fixture:

Fig shows the broaching fixture for making tapered keyway. The workpiece is placed on the horn-shaped portion so that the surface to be broached remain parallel to the broach. Horn is attached with machine face by an adaptor. Its construction is simple.

Broaching fixture

8. Welding fixture:

Welding fixtures are widely used in automobile and aircraft industries. A simple gas welding fixture is shown in fig. To prevent heat loss minimum metal if used in welding area again sufficient support and location are maintained. Welding can be done in a horizontal position can be said as the main advantage of this fixture.

Welding fixture

 Difference between Jig and Fixture: 

Difference between jig and fixture

·       Benefits of jig and Fixtures:

1. Jig and fixtures help in producing the same article in large quantities with a high degree of accuracy.

2. They provide interchangeability at a competitive cost.

3. They eliminate the handling & setting up time & reduces the machining time. Thereby reduces the labour cost and increase the output production and cost of production.

4. They maintain the uniformity of the articles produced.

5. They support & hold the component in position & guide the tool.

6. Advantages of multiple machining can be obtained as Jig & fixture facilitate to accommodate several components in a single setting.

7. It becomes possible to employ unskilled or semi-skilled operator in place of skilled operator.

8. Operations are minimized and simplified.

9. No marking, measuring & other setting is required before machining.

10. Jig and fixture increase machining accuracy.

11. As they produce interchangeable parts, assembly work becomes easy and simple.

12. High clamping rigidity provided by them help to increase speed, feed and depth of cut for machining.

13. They reduce the operator's labour and fatigue.

14. They reduce the expenditure on the quality control of the finished products.

15. They are automizing the process of machining fully or partly and reduces the overall cost of machining.