I'm trying to drill 5/16 diameter holes .750" deep in 321 SS and have used quality carbide drills (MA Ford) and used their reccomended speeds & feeds but the drills still explode after 5 holes. Using coolant as well. I have been pecking at .1" and .05" but neither makes a difference. Does anyone have any experience using cobalt drills or have any suggestions? I understand that this is workhardening material and have been trying to keep the feed up to prevent work hardening but still no success. The holes also have a "lip" around the edges of them after drilling the few that haven't failed. Suggestions?
coolant thru carbide drills? i use mitsubishi carbide drills, coolant thru. rule of thumb is not to peck, just plunge baby plunge. i drill thru 303,304, 316L all day. even plate 304, which i absolutely hate.