Not suitable for key stock (too brittle) but when I need a precision parallel I use large size high speed steel cutting tool blanks like 3/4" or 1" square stuff. The base plate of one of my boring bars has a slightly rough surface, so I put a couple of parallel bars between it and the top of an engine block on occasion. It helps to get a perfectly square alignment with the bore centerline.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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