Eric U
Hot Rolled
- Joined
- Feb 26, 2003
- Location
- Eastern AL
I've got some holes I'm drilling that should really be flat bottomed, and accurate, with chamfer or radius in the bottom corner.
I'm doing this on my lathe right now. The material is 4140 RC 44-45 and I'm trying for a 3/8" diameter hole 1.375" deep. I'm pre-drilling with a cobalt 11/32" drill. I then follow up with a carbide four flute 3/8" endmill with .030" corner radius. The finish is beautiful, and the diameter is right at 3/8", plus 0 minus .0005". The problem is the end of the endmill isn't flat. There is a "cone" left at the bottom of the hole that is about .015" higher in the middle than on the edges.
Any other way to do this easily, and hopefully cheaply? Any source out there for flat bottomed drills? Flat bottomed end-mills with radius or chamfer? Any such thing as a bottoming or end cutting reamer? I can live with a small (1/16") center hole in the bottom of my bigger hole for clearance or non-center cutting purposes. My cobalt drill is already dulling, after only 9 of these holes, so I'm not convinced that I sould be using HSS or cobalt cutting this material. I'd prefer carbide if possible.
Thanks,
Eric
I'm doing this on my lathe right now. The material is 4140 RC 44-45 and I'm trying for a 3/8" diameter hole 1.375" deep. I'm pre-drilling with a cobalt 11/32" drill. I then follow up with a carbide four flute 3/8" endmill with .030" corner radius. The finish is beautiful, and the diameter is right at 3/8", plus 0 minus .0005". The problem is the end of the endmill isn't flat. There is a "cone" left at the bottom of the hole that is about .015" higher in the middle than on the edges.
Any other way to do this easily, and hopefully cheaply? Any source out there for flat bottomed drills? Flat bottomed end-mills with radius or chamfer? Any such thing as a bottoming or end cutting reamer? I can live with a small (1/16") center hole in the bottom of my bigger hole for clearance or non-center cutting purposes. My cobalt drill is already dulling, after only 9 of these holes, so I'm not convinced that I sould be using HSS or cobalt cutting this material. I'd prefer carbide if possible.
Thanks,
Eric