Indicator Stands and Calibration

I have several CI indicator stands, and the Indicators on them are calibrated in our company's system. We have our granite surface plates serviced and calibrated at regular intervals. What about these small CI stands? their surface is about 4" X 6" - what would your protocol be for these?

At the least you should confirm flatness of the platen, and it's probably a good idea (but not critical) to check perpendicularity of the post to the platen.

For flatness checking you can take a small, known good granite plate and do a print with spotting compound to look for hollows or similar wear.

It's funny you bring this up today - I just unearthed a small stand (around a three inch diameter platen) that I've not used in a while and set it up for a part. Has to be five or more years since I needed it...

The function required of an indicator stand is that it holds some type of indicator gage in a stable position relative to a reference base (typically a surface plate or table) that stably holds an object to be measured by the indicator.

The two questions to be asked -- at each and every use of the indicator stand -- are 1) is the indicator stand stable with respect to the reference base, and 2) is the indicator gage, as held by the indicator stand, stable with respect to the reference base?

Verification of stand-to-reference-base and stand-mounted-indicator-to-reference-base stability, to repeat for emphasis, must be verified at each and every use. Calibration stickers don't guarantee that stability.

And for the record, I've used improvised indicator stands when making customer-witnessed measurements of space-flight hardware. Never had a customer express concern about the junkbinium indicator stands, but I've always explained the improvised stands and demonstrated their stability before starting the for-the-records measurements.