Gage Block calibrations

I've a fair amount of gauge block useage behind me and to be honest calibrating them is, or can only be done by the companies that have a dedicated laboratory and the hugely expensive equipment necessary to compare the gauge blocks with their NIST traceable standard gauge blocks...

Laser interferometry is the only way to get satisfactory calibration completed, to any level of confidence... and that's expensive and needs laboratory conditions etc...

Now if you're talking about workshop grade blocks (grade2 / 1) and your company has a calibration set of blocks (00) together with a comparator that can measure or compare with an uncertainty necessary then you can use those blocks as your standard reference blocks and send them away to be checked once a year to a NIST laboratory...

John.

We've been through similar exercise and finaly decided to never calibrate the blocks. It costs too much and does not make sense. It costs almost as much to calibrate as it does to purchase new. Even with external calibration, you still need to replace worn or damaged blocks after you've paid for the calibration.

Each year we remove the old set of workshop blocks, replace those with the metrology set that's done basically no work and buy a new set for metrology.

That way the workshop gets very good quality slips every year, we have valid calibration for metrology set each year. Our system reflects this strategy, so auditors are satisfied.

(Obviously, any damaged or marked slips are removed from the sets, but that is a rare occurence.)

If you follow the principals of calibration, you would still need a higher order reference set to perform your measurements and you would need to have them calibrated off site anyway.

I know that not only for gage blocks, but for some other measuring devices, it is cheaper to buy a new one than to calibrate it. But don´t forget that the real calibration that validates a measure is that performed after, this is the reason of the required periodicity in calibration. You are saying that you still need to replace worn or damaged blocks after you've paid for the calibration. And how the auditors accept that? If you consider that a measuring device can degrade between calibration periods, you should shorten the period, because when you detect a measuring device out of tolerances you must put under suspect all measures performed from the last valid calibration, review them and decide regarding the influence of such measuring deviation.

It seems an easy practice, but a rigorous auditor wouldn't accept it.

Best regards

Very valid point on the intervals instead of just buying new. I agree an auditor should be questioning this. You could be using blocks that have never really been done correctly and off target.

I also think I will just send out then as well.

Thanks,