Fixtures And Jigs ~ MECHTECH GURU

Fixtures And Jigs

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 tools and result faster and accurate machining with consistent quality, functional ability and interchangeability.


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

 Purpose Of Using Fixtures And Jigs:-
conventional drilling machine without using any fixture or jig, the following elementary steps are to be sequentially followed

  1.   cleaning and deburring the blank (disc) 
  2.   marking on the blank showing the location of the hole and its axis on the blank
  3.   punch the centre at the desired location and prick punch the periphery of the hole to be made in the disc
  4.   mount the blank in a drilling vice using parallel block, a small Vee block etc. to provide support and clamp the blank firmly
  5.   position the vice along with the marked blank to bring the hole axis in alignment with the drill axis by 
  •  either adjusting the vise position w.r.t. the fixed drill axis 
  •  or moving the drilling machine table and then locking the table position 
  •  or moving the radial arm and the drilling head, if it is a radial drilling machine 
6.   after fixing the blank, vise and the table, alignment is checked again
7.  if error, like eccentricity, is found to occur then readjustment of location of the hole – axis is to be done before and even after starting drilling
 8.  drilling is accomplished.

The basic purposes of developing and using suitable jigs and fixtures for batch production in machine shops are :-

1.  to eliminate marking, punching, positioning, alignments etc. 
2. easy, quick and consistently accurate locating, supporting and clamping the blank in alignment of the cutting tool 
3. guidance to the cutting tool like drill, reamer etc. 
4. increase in productivity and maintain product quality consistently 
5. to reduce operator’s labour and skill – requirement 
6. to reduce measurement and its cost 
7. enhancing technological capacity of the machine tools 
8. reduction of overall machining cost and also increase in interchangeability.

Jigs and fixtures are manually or partially power operated devices. To fulfil their basic purposes, jigs and fixtures are comprised of several elements:
1.  base and body or frame with clamping features 
2. locating elements for proper positioning and orientation of the blank 
3. supporting surfaces and base 
4. clamping elements 
5. tool guiding frame and bushes (for jig) 
6. indexing plates or systems, if necessary 
7. auxiliary elements 
8. fastening parts 

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