Concentricity Vs Positional tolerance (and their relation to TIR GD&T)

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Posted by Venkataraghavan (203.200.41.196) on January 03, 2003 at 09:49:09:

Hi there,

Seasons greetings and a Happy New year.

I want some good explanation from any of you experts. I have a cylindrical component with 2 diameters. This is a deep drawn and turned Stainless steel component. The drg calls for a positional tolerance of dia 0.15 for the smaller diameter w.r.t. the larger diameter. A few questions now.

Measurement: I mount the component on a mandrel such that the larger dia is located and I then measure the TIR on the smaller dia with a dial indicator.

What does this TIR reading give?
Would this TIR divided by two give me the concentricity?
Is this concentricity the same as the positional tolerance that I want ?
Or is there a specific relation between concentricity and positional tolerance.

If Concentricity and Positional tolerance in this case is same, then why would one want Positional tolerance?

Is the above method of measurement correct at all.

Or should I go for a CMM.

Would appreciate your quick and detailed responses.

thanks

Venkat

Subject: Re: Concentricity Vs Positional tolerance (and their relation to TIR)

Comments:
: Hi there, : Seasons greetings and a Happy New year. : I want some good explanation from any of you experts. I have a cylindrical component with 2 diameters. This is a deep drawn and turned Stainless steel component. The drg calls for a positional tolerance of dia 0.15 for the smaller diameter w.r.t. the larger diameter. A few questions now. : Measurement: I mount the component on a mandrel such that the larger dia is located and I then measure the TIR on the smaller dia with a dial indicator. : What does this TIR reading give? : Would this TIR divided by two give me the concentricity? : Is this concentricity the same as the positional tolerance that I want ? : Or is there a specific relation between concentricity and positional tolerance. : If Concentricity and Positional tolerance in this case is same, then why would one want Positional tolerance? : Is the above method of measurement correct at all. : Or should I go for a CMM. : Would appreciate your quick and detailed responses. : thanks : Venkat

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