Calibration of Optical Comparator Overlays - Radius, Thread and Angle

[Dale D. Barnes]

I have never even thought about calibrating my overlays (Radius, Thread and Angle) until someone found it on a audit. Are these check for wear only? Do they even need to be calibrated? Can someone help me in finding a standard for these I am not having any luck!

Thank you
Dale

[Wes Bucey]

In Reply to Parent Post by Dale D. Barnes

I have never even thought about calibrating my overlays (Radius, Thread and Angle) until someone found it on a audit. Are these check for wear only? Do they even need to be calibrated? Can someone help me in finding a standard for these I am not having any luck!

Thank you
Dale

I'm making an assumption not in evidence that you BUY your overlays from some organization, rather than make them in house. This supplier should be able to lead you to information on how the overlays were calibrated and certified in the first place (at manufacture) and should be able to give you direct information about whether you need to have the overlays calibrated, when, and how to do it.

Almost all manufacturers of optical comparators and other optical measuring devices are very responsive and willing to provide information regarding their products in relation to traceability to NIST.

[Ron Rompen]

Is your comparator used only for visual (i.e. attribute) comparison to templates, or do you also use it for direct measurement (edge detector, or X-Y DRO?)

[kaseyp]

This is a very interesting question. We have similar overlays in my company (Which is currently QS9000 Registered) and have been fine with just labeling the overlays as "No Calibration Required." Our inspectors use them for visual comparisons only. I doubt my Auditor has ever seen the overlays during his audits because we keep them in a drawer. Makes me wonder what he would think.

[davidt]

Our auditor recently had a similar observation; radius overlay charts not in the calibration system and not traceable to a national standard. Our engineers plot the charts using autocad and print on mylar. We use the charts for direct measurement and verification of small parts. Any ideas on how we could address this issue and satisfy the intent of the ISO9001-2000 standard would be appreciated.

Thanks,
DMT

[bmccabe - 2006]

I do the same thing myself here. I have made many overlays, including radii gages, and measure them on our CMM to generate data for calibration. It seems to have satisfied the auditors thus far. Let me know if this helps, or you have more specific questions.

[Ederie - 2007]

After you get the Optical comparator calibrated, (legal source)use your DRO to measure the geometry on the overlay to see if it matches.
Then come up with some acceptance criteria and put a
calibration sticker on the overlay.

[davidt]

Thanks to both of you for the quick responses. The method that Ederie describes will likely work well for us.

Thanks again and regards,
DMT