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Measuring TIR of groove on a cold headed pin Question
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Posted by: wedge

03/03/2004, 11:59:36

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I am trying to measure TIR of a groove that we place on a cold headed part. The issue is I have a 5c collet spin fixture and indicator. Each one has an accuracy which we believe is to great for the tolorence that we are trying to measure. Say on a 1/4 Pin we would have a groove dia .232" with a TIR of .002 and groove width of .039". My spin fixture is has an accuracy of .0005 and my collet has the same accuracy plus the .0005 indicator. I do not believe that it is an accurate enough system to measure the .002 TIR. Any help on this would be great.


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Re: Measuring TIR of groove on a cold headed pin
Re: Measuring TIR of groove on a cold headed pin -- wedge Post Reply Top of thread Forum
Posted by: RandyKimball
03/03/2004, 22:07:54

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In what device did you form the groove? For example, if you made the groove, you should measure the groove roundness in that machine before you remove the pin AND check the TIR of the pin in the same proceedure. If the groove is round and the pin runs within a TIR of .0005 you would have a (you get the rest).
BUT, if you have pins that were grooved elsewhere you need to place the pins in a tied down vee block with one end against a stop and spin the pin in the vee block with the proper indicator anvil in the groove. Remember, if your indicator anvil is not vertical or horizontal to the center line of the pin your reading is not accurate. A good way to correct for this is to place a blade in the groove and read the travel of the blade movement. This could also allow you to multiply the reading for more accuracy establishing the length of the blade from a pivot point to the center line of the pin and to the reading point (a simple lever). This is the best way to build a test fixture for many pins.

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