Calibration procedure for radius gages



I am in the process of writing a calibration procedure for radius gages, for our plant, but have come to a standstill. Can anyone help me out?


Al Dyer


Are you taking about the usual radius gage we have in out pockets, or a more advanced type of gage?



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Are these gages getting a lot of use and subject to wear? My remondation would be to toss them, get a new set that is certified and then just replace the set every few years. It will be more cost effective in the long run that having them calibrated and then buying individual replacement for the worn ones.

Just MHO,



Wipe each gage clean, check for nicks or burrs on the gaging surfaces and dress the edges if necessary, using a hard Arkansas stone. Visually check to make sure there are no flats or interruptions in the gaging surfaces. Lay each gage on a surface plate or other plane level surface to make sure the gage is not warped or bent.

Size and conformity of the radial contour of each gage may be verified using an optical comparator which is equipped with a radi chart

Record any discrepancies or adjustments made on the Gage Calibration Record

The radius gages are acceptable if they exhibit no flats or deep imperfections in the contour surfaces are within 0.005” of the size marked on the gage.

Al Dyer


From a calibration novice:

Did you (or you company) write this calibration procedure, or is it from some formally approved calibration standard that might be part of an A2LA or other nationally approved system?

Has it proved out with your registrar/auditor?

Would you use such a radius gage to approve product for final shipment to the customer? (I guess that is tolerence dependant)

A hand held radius gage capable of .0005 discrimination, not with my eyes!

If I had a radius that tight called out on a print I would think about accepting the job first, then probably use A CMM or laser type gage, rather that a handheld.

Not a dig, just looking for more information.

I like CarolX's idea.



Hi all,
I've seen two methods. A visual (preferable) or touch probe CMM with a lot of hits, or comparison to calibrated pin gages using an indicator for outside radii. A CMM with a touch probe doesn"t work well on the smaller gages. Optical comparators generally aren't accurate enough but help to locate flats.
When you consider the cost of buying new, calibrated gages, you'll say ouch.


I'm not a radius gage expert, but from a calibration management perspective, if you discard a gage rather than recalibrate, as recommended above, don't you lose the opportunity to confirm the gage was in-tolerance, and the chance to recall/retest affected products if it was not?

Al Dyer

Good Point Norm,

I guess it comes down to the variables in each individual company.

Is the gage used for verification of a set-up and not first artical approval?

What is the calibration frequency?

Is the gage mastered before final artical inspection?


I believe that a robust system will use pre-mastered gages to verify the validity of final artical inspection and preclude the need to notify the customer. (hopefully!)

As always, there are holes in the system and if an unverified and/or out of calibration gage is used to verify final product the customer must be notified.

Up front planning on gaging is a must in my view and not enough companies take advantage of the systems that they can set up to ensure that only qualified gages are used to accept final product.

If a proper gaging sytem is implemented the chance of sending nonconforming product is minimized. Prevent, don't detect. In the end, protect the customer, they pay your bills!



AJ's procedure is right on the money. We have been calibrating them this way for 10+ years. Under normal use these kind of gages last for decades so repurchasing is not necessary. Al the "Tolerance" AJ referanced was .005 not .0005.
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