Jigs and Fixtures used to hold the Work Piece

 

Definitions 

• Jig:

A device that holds the work and locates the path of the tool.

• Fixture: A device fixed to the worktable of a machine and locates the work in an exact position relative to the cutting tool.

•  What are Jigs and Fixtures.

    Anything Which is used to hold a work piece in a desired location.

  e.g.
  

  • Locate parts for precision
  • Repeating process on a series of parts
  • Holding parts for machining, painting, assembly

   
  

   

   Types of jigs
   Following are the seven different types of jigs.
  1. Template jig
  2. Plate jig
  3. channel jig
  4. Diameter jig
  5. Leaf jig
  6. Ring jig
  7 Box jig 

  1. Template Jig

  

  The template jig is the simplest of all the types. A plate 2 having holes at the desired positions serves as a which is fixed on component 1 to be drilled. The drill 21 is guided through these holes of the template 2 and the required holes are drilled on the work piece at the same relative positions with each other as on the template. A template jig is shown in the figure.

  2. Plate Jig

  

  • A fixture holds and positions the work but does not guide the tool. Whereas a jig holds, locates and as well as guides the tool.
  • The fixtures are heavier in construction and are bolted rigidly on the machine table. Whereas the jigs are made lighter for quicker handling, and clamping with the table is often unnecessary.
  • The fixtures are employed for handling work in milling, grinding, planing, or turning operation. Whereas the jigs are used for holding work and guiding the tool particularly in drilling, reaming & tapping Operations. 

  A plate jig is an improvement of the template jig by incorporating drill bushes on the template. The plate jig is employed to drill holes on large parts maintaining accurate spacing with each other. A plate jig is shown in the above fig. 

  3.Channel Jig

  

  The channel jig is illustrated in the fig. It is a simple type of jig having a channel-like cross-section. The component 1 is fitted within the channel 4 and is located and clamped by rotating the knurled knob 5. The tool is guided through the drill bush 3. 

  4. Diameter Jig

  

  The diameter jig is shown in fig. It is used to drill radial holes on a cylindrical or spherical work piece. The work 1 is placed on the fixed V-block 6 and then clamped by the clamping plate 7 which is also locate the work. The tool is guided through the drill bush 8 which is set radially with the work.

  5. Leaf Jig

  
  

  The leaf jig is illustrated in the above figure. It has a leaf or a plate 13 hinged on the body at 11 and the leaf may be swung open or closed on the work for loading or loading purposes. The work 1 is located by the buttons 10 and is clamped by set screws 12. The drill bush 3 guides the tool. 

  6. Ring Jig

  

  The ring jig is shown in the above figure. It is employed to drill holes on circular flanged parts. The work is securely clamped on the drill body and the holes are drilled by guiding the tool through drill bushes.  

  7. Box Jig

  

  The box jig is illustrated in the above figure. It is of box-like construction within which the component is located by the buttons 18. The work 1 is clamped by rotating the cam handle 19 which also locates it. The drill bush 3 guides the tool. The box jigs are generally employed to drill a number of holes on a component from different angles.  

   Type of Fixtures

   1. Turning Fixture

  2. Milling Fixtures 

  3. Broaching Fixtures
  4. Indexing Fixtures

  5.Grinding Fixtures

  6. Tapping Fixtures 

  7. Tapping Fixtures 

  8. Duplex Fixtures 

  9. Welding Fixtures 

  10. Assembly Fixtures  

  1. Turning Fixtures: These fixtures are generally mounted on the nose of the machine spindle or a face plate, and the work pieces held them. Whenever necessary, the fixture may have to be provided with a counterweight or balance the unbalance fixture.  

  
  

  2. Milling Fixtures: Milling fixtures are typically mounted on the nose of the machine spindle or a face plate, and the work-pieces held them.The table is shifted and set in proper position, in relation to the cutter. The work-pieces are located in the base of the fixture and clamped before starting the operation.

   

   

  3. Broaching Fixtures: Broaching fixtures are used on different types of broaching machines to locate, hold and support the work pieces during the operations, such as key way broaching operations, such as key way broaching, hole broaching, etc. 

  
  

  4. Indexing Fixtures: Several components need machining on the different surface such that their machined surface surfaces or forms are evenly spaced. Such elements are required to be indexed equally as many as the number of surfaces to be machined. The holding devices (jigs or fixtures) used are made to carry a suitable indexing mechanism. A fixture carrying such a device is known as an indexing fixture. 

   

  5. Grinding Fixtures: These fixtures may be the standard work-holding devices, such as chucks, mandrels, chuck with shaped jaws, magnetic chucks, etc.

  6. Boring Fixtures: This fixture incorporates almost all the prevailing principles of jig and fixture design, their construction need not be as sturdy as that of the milling fixtures, because they never have to bear as heavy cutting loads as involved in milling fixtures, because they never have to endure as heavy cutting loads as involved in milling operations.

  7. Tapping Fixtures: Tapping fixture is specially designed to position and firmly secure identical work-pieces for cutting internal threads in drilled holes in them. Odd shaped and unbalanced components will always need the use of such fixtures, especially when the tapping operation is to be carried out repeatedly on a mass scale on such parts.

  8. Duplex Fixtures: It is the name given to the fixture which holds two similar components simultaneously and facilitates simultaneously machining of these components at two separate stations.

  9. Welding Fixtures: Welding fixtures are carefully designed to hold and support the various components to be welded in proper locations and prevent distortions in welded structures. For this, the locating element need to be carefully; clamping has to be light but firm, placement of clamping elements has to be clear of the welding area. The fixture has to be quite stable and rigid to withstand the welding stresses.

   10. Assembly Fixtures: The function of these fixtures is to hold different components together in their proper relative position at the time of assembling them.
  

   

  Uses of Jig and fixture

   

  • Reduce cost of production.

  • Increase the production.
  • To assure high accuracy of parts
  • Provide for interchangeability
  • Enable heavy and complex parts to machine
  • Reduced quality control expenses.
  • Increased versatility of machine tool.
  • Less skilled labor.
  • Saving labor.
  • Partially automates the machine tools
  • Use improve the safety, accidents low