Any suggestions on getting good finishes on 4140? I tried making some 7/8" dies several years ago. Horrible finish! I've since read that it doesn't machine well.
Quote from: customcutter on June 27, 2022, 02:11:12 PMAny suggestions on getting good finishes on 4140? I tried making some 7/8" dies several years ago. Horrible finish! I've since read that it doesn't machine well. KC-810, KC-850 inserts used to work pretty good. I do not know what the equivalent would be today. Sulfurized lard oil for cutting fluid helps and factory heat-treat, (RC 28 hardness).