Oldwrench
Titanium
- Joined
- May 21, 2009
- Location
- Wyoming, USA
Back in 2017 Matt@RFR posted this:
I found Matt's really clear and specific recommendation with a PM search. We are ordering two turning centers with 290psi coolant to drill .3906 blind holes 5.5xD deep in 41L42 and not have to peck. We'd have to use an 8xD drill (MWS03906X8DB) because I can't find anything between 5xD and 8xD.
Reading the directions in the Mitsubishi coolant thru drill catalog, they seem pretty adamant about using a 2-3xD guide hole using a flatter point (MZS03906MB), slowing down near the bottom and then again prior to leaving the hole. Now I totally get the need to slow down to protect the corners of a carbide tool from vibration-induced chipping, but a guide hole would require a second coolant-thru drill and would occupy another turret station already committed to another tool.
Trueness is not awfully important, but we do need to hold the runout to no worse than an ordinary drill starting in a 90° spot. Since the thru-coolant carbide drill would be a lot stiffer than HSS, could we just start the hole from a faced end with maybe a very small spot just to make sure it doesn't start on a tit?
I have to wonder whether applying TWO expensive drills will really end up with a lower cost per hole over several thousand parts, versus our current peck method with HSS drills and external coolant. Can Matt or anyone chime in with experience relevant to this? Thank you.
We run a 10mm 10xD Mitsubishi TSC drill in 4140PH at 375 SFM and .010 IPR. 3" thru, no peck, no spot, 300psi. One drill is good for about 600 of those parts. They'll go much faster, just depends on your tool life needs.
I found Matt's really clear and specific recommendation with a PM search. We are ordering two turning centers with 290psi coolant to drill .3906 blind holes 5.5xD deep in 41L42 and not have to peck. We'd have to use an 8xD drill (MWS03906X8DB) because I can't find anything between 5xD and 8xD.
Reading the directions in the Mitsubishi coolant thru drill catalog, they seem pretty adamant about using a 2-3xD guide hole using a flatter point (MZS03906MB), slowing down near the bottom and then again prior to leaving the hole. Now I totally get the need to slow down to protect the corners of a carbide tool from vibration-induced chipping, but a guide hole would require a second coolant-thru drill and would occupy another turret station already committed to another tool.
Trueness is not awfully important, but we do need to hold the runout to no worse than an ordinary drill starting in a 90° spot. Since the thru-coolant carbide drill would be a lot stiffer than HSS, could we just start the hole from a faced end with maybe a very small spot just to make sure it doesn't start on a tit?
I have to wonder whether applying TWO expensive drills will really end up with a lower cost per hole over several thousand parts, versus our current peck method with HSS drills and external coolant. Can Matt or anyone chime in with experience relevant to this? Thank you.