Stuart Caruk
Stainless
- Joined
- Feb 20, 2007
- Location
- Ridgefield, WA
While working up an old process on a new (to us) machine I smoked a brand new 30xD coolant fed carbide drill on it's second hole. I've run these (not quite as deep though) on an Integrex using the manufacturers specs.
The manufacturer recommends around 262 SFM and .010 FPR for both the pilot drill and the 30xD drill. Typically I face the entry flat with a CEM since the holes are all at multiple angles. I pre drill the start hole to 2xD which since I'm using 5/16 drills is .750" deep. Then I switch to the 30xD drill, enter the hole at 1000 RPM with high pressure coolant on at .010 FPR, and go to .011 short of the predrilled hole or .739" deep. Then I pick up the speed to the 3020 (roughly) RPM and feed to depth at the recommended speed. Then I reduce the RPM to 50 RPM and withdraw at 75 IPM out of the hole. ON the Integrex, the spindle has no gearbox so the speed change is instantaneous AND it has spindle speed confirmation so the drill won't feed until the spindle is up to the commanded RPM.
On our Horizontal, the spindle shifts at 2500 RPM, so the spindle stops, changes gears, and then goes to 3000 RPM and feeds into the hole.
I did the first trial hole at 6" deep, and it worked great. The second hole broke the drill about 2 1/2" deep. There was plenty of coolant, so I'm guessing the spindle might not have been up to full speed before the feed rate began. These drills are pretty spendy so I'd prefer not to bust a bunch of them, but they are waaaaaaay faster than peck drilling with a cobalt drill, so it's worth working out the process.
I can see 2 possible solutions, and I'm curious to hear what the deep hole drill experts do.
Option 1 would be to simply add a G4 dwell after the speed change to ensure the spindle is up to speed before feeding in. If I add a 3 - 4 second pause, will it damage the flutes to simply spin .011 off the bottom of the hole? It's a 4 margin KM drill if it matters.
The other option would be to pick up the speed, pause, and start at a slower feed rate, increasing the feed rate as the drill becomes established in the hole.
The material is 4140 prehardened to 32 Rockwell, and I need to go 9.777" deep. I know that's cheating the drill, but the flutes are long enough and I figured I'd go to 9.4", retract almost all the way out of the hole, then feed back in for the last wee bit to make sure the flutes don't plug up.
Curiously,
Stu
The manufacturer recommends around 262 SFM and .010 FPR for both the pilot drill and the 30xD drill. Typically I face the entry flat with a CEM since the holes are all at multiple angles. I pre drill the start hole to 2xD which since I'm using 5/16 drills is .750" deep. Then I switch to the 30xD drill, enter the hole at 1000 RPM with high pressure coolant on at .010 FPR, and go to .011 short of the predrilled hole or .739" deep. Then I pick up the speed to the 3020 (roughly) RPM and feed to depth at the recommended speed. Then I reduce the RPM to 50 RPM and withdraw at 75 IPM out of the hole. ON the Integrex, the spindle has no gearbox so the speed change is instantaneous AND it has spindle speed confirmation so the drill won't feed until the spindle is up to the commanded RPM.
On our Horizontal, the spindle shifts at 2500 RPM, so the spindle stops, changes gears, and then goes to 3000 RPM and feeds into the hole.
I did the first trial hole at 6" deep, and it worked great. The second hole broke the drill about 2 1/2" deep. There was plenty of coolant, so I'm guessing the spindle might not have been up to full speed before the feed rate began. These drills are pretty spendy so I'd prefer not to bust a bunch of them, but they are waaaaaaay faster than peck drilling with a cobalt drill, so it's worth working out the process.
I can see 2 possible solutions, and I'm curious to hear what the deep hole drill experts do.
Option 1 would be to simply add a G4 dwell after the speed change to ensure the spindle is up to speed before feeding in. If I add a 3 - 4 second pause, will it damage the flutes to simply spin .011 off the bottom of the hole? It's a 4 margin KM drill if it matters.
The other option would be to pick up the speed, pause, and start at a slower feed rate, increasing the feed rate as the drill becomes established in the hole.
The material is 4140 prehardened to 32 Rockwell, and I need to go 9.777" deep. I know that's cheating the drill, but the flutes are long enough and I figured I'd go to 9.4", retract almost all the way out of the hole, then feed back in for the last wee bit to make sure the flutes don't plug up.
Curiously,
Stu