GD&T Perpendicularity

[metman]

In the GD&T workbooks it says to subtract the perpendicularity tolerance from the minimum hole size to establish Vc = gauge pin dia.

For example in our case we have a .6240+ -.0005 hole and we are calling out .001 perpendicularity with max mat'l condition. Therefore Vc = .6240-.0005 -.001 = .6225.

So now you use a .6225 gauge pin that has a dia tolerance acceptable to internal quality standards and this pin is pressed into a hole in a plate to use as a perpendicularity gauge. What about this gauge? What establishes the accuracy of perpendicularity of the gauge? In other words, what level of precision of perpendicularity is required for the gauge?

In our workplace I believe the question is answered by the fact we are using a Faro Arm but what if we did not have a Faro Arm?

Jesus is THE life,
Leonard

 

[GDTP]

Leonard,

Here's what I do in these situations. Determine the pin's VC (which you've done), then determine the appropriate tolerance for the pin diameter (usually less than or equal to one-tenth of the product tolerance, and since this is a go gage the tolerance would all be on the plus side). Next, give the pin a zero perpendicularity tolerance at LMC. This assures that the gage will not accept a bad part and will only have a minimal risk of rejecting a good part. Let me know if you have any questions.

Curtis