Calibration Services - NIST


We currently use an external calibration service that comes to our facility. Another quality engineer has recently gone down a rabbit hole and is accusing our calibration service of being "incompetent" and not following standard protocol. This appears to stem from one calibration cert not having upper and lower tolerances provided for a digital micrometer calibration. We have used this company for roughly 10 years and have not had any quality issues stemming from gage calibration in the past. The quality director has given me the assignment of looking over our calibration certs to determine if there is any reason for the other quality engineer to go as far as stopping payment on a check to the calibration company until upper and lower tolerances are provided on the cert. They are accredited and use NIST standards as basis for their testing.

Is there a process I can go through to determine if our calibration provider is using the correct NIST test methods as they are listed on calibration certs? This would at least give me a starting point to determine if there are more pressing issues than a tolerance limit omittance for one single calibration cert.

I'm fine with vetting potential issues with suppliers however, this appears to have some underlying witch hunt elements generated from a soon retired employee (busy work to keep themselves occupied).


Trusted Information Resource
Is the company you use certified to ISO 17025? If yes, I would think the certification of ISO 17025 would be enough unless there are issues raised during the outside certification company.

If they are not certified to ISO17025, what are the using as their method? That would be the direction I would start looking.


In lieu of a upper and lower tolerance listed, is there a required tolerance given as a percent? (ie instead of the tolerance listed being +/- .001 inch is there something indicating a percent (+/-0.1%) .


Involved In Discussions
NIST procedures aren't the only game in town. Many use procedures from GIDEP (typically US military), or from the manufacturer. The critical thing is that the procedure is validated. If the lab is accredited, it is (very likely) that the procedure has been validated.

I would first call the cal lab and ask them about it. It could have been a simple mistake. If the co-worker wants to make a big deal of it: issue a CAR to the cal lab. They should have a process to follow, and it should involve keeping the complainant informed.

You could also audit the cal lab: Ask them for a couple hours of time, and walk through the measurand in question: From receiving documentation to applying the procedure, and issuing/authorizing the cert. That shouldn't take more than 2 hours. If there are gaps, they would be exposed.

Withholding payment for an otherwise valid service is counterproductive in my experience. It just comes across as petty. The cost in time to resolve something like this far outweighs the $150-ish for the cal activity. You will either pay them anyway for service provided, or likely pay them as a "go away and don't bother us again" if you are switching labs.


Starting to get Involved
"This appears to stem from one calibration cert not having upper and lower tolerances provided for a digital micrometer calibration."

Depending on what you mean by "having tolerances": This is more than a calibration, which is giving you a deviation with uncertainity.
If they didn't give you their uncertainity, which might be seen as "their tolerances", well, yes, job not done by lab.
Do you expect them to compare to the gauge tolerance classes? Maybe you need to tell them, maybe it wasn't done when ordering this single time. But it would be a proper calibration, allowing you to evaluate its fitness for the task. (Its not the cal lab that needs to use your gauge to anything.)


Quite Involved in Discussions
What was on your purchase order to the lab for the calibration? Did you specify that you wanted a NIST approved method, manufacturer's calibration or not even specify any requirements but just plain "calibration of...." ? Did you include supply of a certificate of calibration on the purchase order?
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