cuttergrinder
Hot Rolled
- Joined
- Mar 16, 2007
- Location
- Salem,Ohio
I had a little job today where I needed to slot some ar400 plate. It is basically a rectangular plate with 27 slots 3/8" wide by 2 1/2" long. It resembles a floor drain plate but I'm sure that is not what its for. The plate is 3/4" thick and the slots go all the way through. I thought the endmill would have trouble plunging this ar400 so I drilled the end of all the slots. Then I tried to mill the slots with a 5/16 carbide endmill and then I was going to finish with a 3/8" endmill. I tried a .100" depth of cut at 12 in/min and 3000 rpms. That quickly broke a cutter. Then I tried .075" depth of cut and slower feed. Still broke a cutter after about 2 slots. I had the best luck with 1400 rpm and 3 in/min feed. I still can only get about 3 slots before the cutter breaks. I gave up and need help. Lol What seems to be the problem is that the edges of the holes that I drilled are work hardened. I plunge into the drilled hole and it makes noise when it starts to mill longitudinally until it gets through the hardened edge of the hole. I drilled the holes with a 11/32 high speed drill but for some reason it work hardened the edges of the hole. By the time I get one slot milled out the last .100 of the endmill is about toast. Any help would be appreciated. We might end up getting the slots water jetted.