Guys, we were tapping some mild steel pieces today in a JohnFord CNC mill today and I am getting torn and rough threads. We are ridged tapping them and using light colored cutting oil. They are drilled with a 7/16, then run thru them with a pipe reamer, lightly chamfered, and tapped. The tap is a gold(TIN?) coated brand new tap, and they are running them at 180 rpm. Seems like poor steel and the parts have been torched out. They are small parts and a production type job.
Any ideas or suggestions? I have alot of ideas, probably silly ones, so wanted to ask. Thinking of trying a slower rpm and feed...maybe relieving some of the tap threads on the back side so there isnt as much engagement if that makes sense, and thought about a heavier oil, maybe with sulfur in it. Was wonder also if you could tap it not quite to depth, then go back slightly deeper as a finish cut kinda? Since it uses a synchronized tap cycle thought about that...
Thanks for any ideas... Thanks.