Hi Steve,

I enjoyed reading your post, and agree with you on every point except where you figure I know more than I let on about hardness testing.

Could be I understand the concepts in a bookish sort of way, and can relate them to things I've bent or broken over the years, but as for real experience -- I've never been around the other side of the counter in a machine shop.

So, I suppose a photo is helpful, but some things just need hands on experience. Looks like Mick has zeroed in on the problem nonetheless, and given the attention, I'd guess this bolt breaking had some expensive consequences. I learned a lot just reading this thread!
--
Art Benstein near Baltimore

What engineers say and what they mean by it:
"Drawing release is lagging."
Not a single drawing exists.