Plug Gage Calibration - Manufacturer's Certification vs. Calibration Laboratory



Plug Gage Calibration

We have plug gages calibrated once a year from an outside lab. New plugs coming in are requested to have certification with them. I use this certification as assurance the gage is good until the following due date for calibration for all the plug gages. Sometimes this can be a month; sometimes almost a year.I do this because of cost and maintenace issues with them going in and out at different times. Will I take a hit for this? I realize certiciation is not calibration. If I state in my procedure that I do this; am I in compliance? Thanks!!!

Jerry Eldred

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Super Moderator
If you have a calibration (certification) interval for your plug gages, the requirement is that you have them certified at intervals not greater than your prescribed interval. If you have a one year calibration (certification) interval as your established interval, they must be calibrated at intervals no greater than that. If you certify at intervals of less than your prescribed interval, I dont see a problem with that.

From a metrology perspective, the questions that do come to mind are...

1. How did you establish the interval? Is it based on a degree of confidence that the plug gages will remain in tolerance for your interval (once per year)? I think that is probably the more likely quesition in your situation. Bottom line on that point, be sure you have a valid interval. And be sure you calibrate no longer than your established interval, either in terms of time, or number of uses.

and the second issue is your certificates...

2. Are the certificates valid? That is, do they contain needed information, and are they from a somehow approved calibration source (audit, certified by an accredited body, etc.).

Hope this is of some help. Please feel free to send further questions if I didn't cover your question adequately.



Your opinion matches mine perfectly. I needed to hear it from someone else.
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