To calibrate or not to calibrate

[JoshSaxon]

Hi,

I am looking to get some outside micrometers calibrated by an external lab.. My shop does not have any certifications, and we are pretty new, so its our first time doing this. My question is, do we calibrate our micrometers, our mic standards, or both? If we calibrate both and check the mic using the standard and they are different, what do we do? Is it unnecessary to calibrate the mics because the standards are calibrated if we check our mics against the standards before each use? Our gauge tools are pretty new so is it acceptable to check them against an calibrated mic/mic standard and not get them calibrated?

Hoping you all can shed some light on this. Thank you

 

[Ed Panek]

A few questions

1) What does your risk analysis indicate the pain the product would suffer as a result of no/wrong calibration?

2) What would your customers (& you & your company) expect?

Uncertainty is present in every product and company. Typically companies try to remove as much uncertainty as possible but there are diminishing returns after time.

 

[hogheavenfarm]

just get a set of calibrated gage blocks, check mics against those, record readings taken and calibration source (the gage blocks). Note any discrepancies in the readings per mic. Thats the simple version, you can expand on that as your needs indicate. ID the mics separately so you can know which ones read differently and watch for variances over time. This is greatly condensed, but you can research and grow into it. As Ed said, make sure you understand what the results would be if you shipped out of spec material, that will always be your focal point.

 

[John Predmore]

My question is, do we calibrate our micrometers, our mic standards, or both? If we calibrate both and check the mic using the standard and they are different, what do we do?

The standard is calibrated to a tighter tolerance than the measuring device. There are different grades of gage blocks with different tolerance specs. The grade you choose depends on your needs. If the more exacting grade of blocks is chosen, you must keep them in a temperature-controlled room, wear gloves when handling, and follow stringent instructions when they are used as a reference. If your standard block is ever dropped or mis-used, you will immediately send the block(s) to be re-calibrated, without regard to the due date on the calibration sticker/certificate.

Verify before use is an allowable option within ISO9001 section (7.1.5.2.a Measurement Traceability) but your company is still accountable to explain how you ensure your measurement resources are suitable and reliably maintained. If you choose to verify your micrometer before use with gage block standards, your company should have a procedure (or work instructions or a chart or whatever format works for you) how much deviation is allowable before the measuring device is removed from service for adjustment or repair.