Calibration Sphere

[Mike Larson]

Just curious to find out how often a calibration sphere should be sent out for calibration to
verify size and roundness. Our 3 C.M.M.'s are calibrated weekly with this ceramic sphere.
Should the calibration of the sphere be yearly? Once every 3 years? Once every 5 years?
Thanks for your input !

[jmgreen]

I send ours out once every two years.

[JEFMAN]

Never send it...
Maybe I'm wrong, but I believe that uncertainty of laboratories is greater than the difference that they could find between two calibrations...

[ir a programmer]

Never have sent one, never had a question about it.

[Nano Vujkovic]

I would be more worried about metal sphere. Ceramic holds shape well (it's very rigid) and cannot be dented like metal can (which is quiet elastic when compared to ceramic).

[Poleaxe]

Never send it...
Maybe I'm wrong, but I believe that uncertainty of laboratories is greater than the difference that they could find between two calibrations...

+1

[jmgreen]

Yeah, I didn't used to send ours but got bi*ched at by the TS auditor a few years back and decided it wasn't worth it to argue, so now I send it out every 2 years.

[Poleaxe]

Never send it...
Maybe I'm wrong, but I believe that uncertainty of laboratories is greater than the difference that they could find between two calibrations...

+1...and there is a very good reason for that. I had 2 calibration spheres & for a while I complied with the 'Quality Directives' from above & sent the unused spare out each time.

Very amusing to ponder the results & accompanying certificates when it came back. Quite often it dipped out of tolerance & then miraculously back in again next year.

They never did find out but I did have to let the Quality Engineer upstairs in on the escapade as he had been instructed to conduct ‘Minitab’ GR&R studies on the results… again to comply with some ‘know it all’ customer’s QA department.

[John Riggins]

Some auditors are picky about it, some aren't.
Never had an issue til last year.
Now the spheres are on the calibration list.

[Mike Larson]

My primary concern was traceability if the ISO auditor would question when the spheres were last calibrated.
We do have the original Certs. from Brown & Sharpe and Renishaw.
Thanks for all of the input !