Gage Block Grade 1 - Calibration

Chrifer said:

Scanton, It is not that expensive, I actually found a very good price to do so, but unfortunately my boss does not understand that. She believes is so simple and can be done with a caliper or micrometer in our lab . I told her several times that there is a procedure to follow and it is normalized as well and still she doesn't care at all. So, I will give a try with the Zeiss machine and see what I can obtain . However, I am fully aware that Uncertainty will be larger in this case thought .

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Maybe if you show your boss that doing the "calibration" of the blocks yourself will cost more than sending the set out, and that you will be tying up the Zeiss machine, and you will need to spend the time generating calibration records for the blocks, etc., then she might change her mind.
That is on top of it being absolutely stupid to see every lab in the world using gauge blocks to calibrate micrometers and calipers, but she expects to be able to do the opposite.

Chrifter: We don't worry about the Uncertainity error - our tolerances are so large compared to the potential error of our machine that we can afford to ignore them.
I still send them out for an external calibration every 5 years, more as a sanity check than anything else.

The cost of calibrating our master gauge block set is more than the cost of 4 hours of my time, so if in 5 years it took me 4 hours or more to calibrate these myself, it would cost my company more money than sending them away.

If the person above you doesn't have enough of a technical understanding to grasp why this is not the best solution, then reasoning with them on a purely financial basis (as suggested by dwperron) could be the way to go.

Thats a good point Scanton. Doing the gage blocks 'in-house' is an alternative, but it is an expensive one. Some bean counters will contend that 'well, we're already paying you anyway' without considering the OTHER work that you have to/could be doing.

There is absolutely no reason you cannot calibrate your gauge blocks with your CMM. You will no longer have a set of Grade 1 blocks, but something with higher uncertainty; which could well be higher than is useful to calibrate micrometers. You will need to calculate the measurement uncertainty that you have of measuring the blocks with your CMM. A spreadsheet made by the Canadian national lab (NRC) is a nice simple tool to use.

The direct link is here: https://nrc.canada.ca/sites/default/files/2019-03/uncertainty_budget_template.xls

Here is a short thread on the subject: Uncertainty Budget for CMM

Thanks for the link greif. I will have to take a good look at it, and see how to apply it to our processes.