Hi Pete. Thanks for the rule of thumb. So, this rules out the use of files for making square or circular cross-section tools from?
I did a calculation for an average sized file from my "free" stash:
scale=2
15/16/(5/32) 6.20This is more than twice as bad as 3:1, and this is with the teeth not ground off. That means that a file is probably unsuitable for edge upsetting, unless one is willing to slop everything over, cover it with flux, and try to get it to stick together, which may have been what the maker of that E-bay pictured file chisel did. Left a lot of "interesting" texture.
Thanks, Eric