Traceability to the Thimble of ID (inside diameter) Micrometers and Depth Micrometers

[Bob the QE]

I am looking for ideas on how to make stems for depth mic's and ID mic's traceable back to the thimble. Or maybe they don't need to be but I would think they would. You covers always provide great information and ideas so I am sure I will get either or from you.

Thanks in advance.

[Coury Ferguson]

Any comments?

[brobinson]

Yes, you are absoutely correct on your traceability assesment. Each depth rod and each id rod from a set are calibrated to a single micrometer head.

So, a set of depth mics has a micrometer head and typically 3, 6 or 9 rods. Each rod has the zero setting adjusted at the low end with the micrometer head.

For every ID mic set, wether it be tube mics or rod mics, each rod is has the zero setting adjsuted at the low end with the micrometer head.

For tracability, we acid etch a control number on every rod and the micrometer head in a set. It is actually a very easy process.

Do Not!! use a rod from someone else's set for measuring or calibrating purposes. You will have false readings.

In addition to setting the zero on each rod, the calibration for a gauge set should include a lead error check on the head itself. This will verify the integrity of the gauge by checking for wear or slop on the lead screw. I've seen some ID mic sets have lead error readings up to .0008". ID mics should have a slight drag on the turning of the head as opposed to smooth movement on a depth or od micrometer. We have a lot of operators that will loosen the lead nut on the shop floor, essentially voiding the calibration.

If you have any other questions, or I just confused you please let me know and I'd be glad to help.