Well Duh.....

Last winter I was trying to grind an old 3/8" endmill shank to 1" length to be used as a standard to calibrate my 1-2" micrometer. I have a tenths indicating micrometer, and two others to cross-reference it to, so I was confident I could get it within a tenth and it would good enough to calibrate my other micrometer. I figure I had a good Starrett V block, decent grinder, and with patience do a halfway decent job. I was wrong.

No matter what I did, or how clean everything was I just couldn't get the rod ends parallel I forget the measurements but it was around a tenth off. So I stuffed the bit in a drawer and hoped to forgot about it.

Today I had the surface gauge and a ball bearing out to check squareness of some pieces, and was going to use that same V-block as a squarness master (verify two sides parallel, zero indicator, flip, and split your reading straddling the zero mark and in theory perfect zero) and it turns out the V-block was out .001" in squareness over it's 1.5-1.75" length. I got the V-block from a late family relative, I was the one to unwrap it from it's wax coating and use it for the first time. It's not worn out or abused except for the usual wear or ding. I guess you should never take anything for granted and inspect it before you use it.

As AvE would say "It just never ends"

Count yourself as one of the fortunate ones who still knows HOW to check things. I sometimes really do fear that with all our time-saving, accuracy-improving, idiot-proofing world we have created something very, very dangerous. When few will actually know how to check if the spreadsheet is right, how to know if a dimension seems plausible, how to verify that a claim is true. Scary.

-frank

Reminds me of that prophetic story by Robert Heinlen (I think) where the army grunt used "mental arithmetic" and always got the right answer much to the surprise of his seniors.
I cant remember all of it as it was a long time ago I read it but that part always stuck in my mind.
Watching cashiers surprise when you hand them the correct money because you added up all the purchases in your head.
Even better when they double ring an item and you query the total and are correct.