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Joe, I hope you don't get mad but I'm going to offer a little different perspective on what you have stated, -with the exception of your last paragraph which I think is true.
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Not mad and it appears you have taken almost all I have said and added to it. THIS is the purpose of the board.
And it has been um, (gosh) 40 years since I went through my little trial by crankshaft.
I think back to "truing" the center in my 1906 Flather lathe and I realize I was using the flywheel flange for truing, so no skim cut required - but it did help the crankshaft straightener get a better bite and do a better job.
Generally my experience with engine mains mirrors yours - but there is this "theory" about grinding the minimal amount and to do so may require relocating the center. Now with "aftermarket cranks" fully available perhaps the need/desire is not so much?
I will admit to not doing engines every day (fortunately) and I have the ultimate respect for anyone who did - or does. Including that Knight Engineering of Pigeon Cove dude who brought me the bad news of a bent crank. He like most others in his trade did the best he could with what he was given.
And, yes, cranks can bend merely in sitting - I have one on the floor right now on its side which every day I pass and think I should do better to "keep 'er straight." But not to the tune of 0.015 like my original engine crank showed AFTER grinding. This was the product of a grinder who didn't give a $*it.
Maybe it was his bad day?
Joe K