JP Machining
Stainless
- Joined
- Jul 15, 2006
- Location
- Wisconsin
I'm pulling hair out over this and at my wits end.
Hurricane bolts (sidewalk bolts) 18-8 stainless. 3/8"-16 threads, 1/2" long. All I need to do is drill a 1/4" hole through it length wise. Problem is the hole is so close to thread minor that any work hardening and the last 2 threads get pushed out and a nut no longer threads on. If I program any amount of peck or chip break I get massive thread deformation and looks like holes walks off center line but its actually just bending the thread section. Cheap chinesium stainless.
I tried carbide drills from Mari, chipped on first part. Best luck so far is a Tin coated cobalt stub length drill from Mcmaster. I once was able to get 40 done on one bit, now I cant seem to get 5 done and just deforming threads too much.
I dont have through tool coolant which is probably the biggest detractor. I have soft jaws cut in lathe chuck to grab head of bolt and clearance over threads so as not to damage them from jaws. Center drill, then go in with the 1/4" drill. My best luck was at 600 rpm and 0.0035" ipr, now down to 450 rpm same feed and still issues.
I thought about flipping them around so threads stick out of chuck, but problem there is lengths vary by quite a bit so hard to put proper spot drill mark in without facing first and then more issues arise.
I should of just quoted turning them from solid then could drill the hole first, then thread. I have something like 150 more to do with more batches to come if I can do it.
Hurricane bolts (sidewalk bolts) 18-8 stainless. 3/8"-16 threads, 1/2" long. All I need to do is drill a 1/4" hole through it length wise. Problem is the hole is so close to thread minor that any work hardening and the last 2 threads get pushed out and a nut no longer threads on. If I program any amount of peck or chip break I get massive thread deformation and looks like holes walks off center line but its actually just bending the thread section. Cheap chinesium stainless.
I tried carbide drills from Mari, chipped on first part. Best luck so far is a Tin coated cobalt stub length drill from Mcmaster. I once was able to get 40 done on one bit, now I cant seem to get 5 done and just deforming threads too much.
I dont have through tool coolant which is probably the biggest detractor. I have soft jaws cut in lathe chuck to grab head of bolt and clearance over threads so as not to damage them from jaws. Center drill, then go in with the 1/4" drill. My best luck was at 600 rpm and 0.0035" ipr, now down to 450 rpm same feed and still issues.
I thought about flipping them around so threads stick out of chuck, but problem there is lengths vary by quite a bit so hard to put proper spot drill mark in without facing first and then more issues arise.
I should of just quoted turning them from solid then could drill the hole first, then thread. I have something like 150 more to do with more batches to come if I can do it.