I think it would really depend upon the type of heat treatment that was given craigd. What might not seem to significantly deter cutting with a 10" mill bastard file or a stout milling cutter might easily dull or damage the fine engraving tools kutter is using. But the exact same steel that was hardened, but not drawn, might be very difficult to file or mill. The metallurgical CHEMICAL analysis of a sample of steel is very important, but does not tell us everything. Different heat treatment can make a huge difference in machinability and performance. The exact same grade of steel might bend, flex, or shatter like glass, depending upon annealing, hardening, and tempering. You can experience all of the above while learning to make springs.
