Re: Tell me more about speed
Maybe a stupid question, but what are the proper speeds for steel, aluminum, and wood.
When using a variable speed handheld how do you judge the proper speed?
Thanks
As an auto mechanic I've been up against this problem for years. It's a "seat of the pants" thing. You've got to remember a few ground rules.
The harder the material, the slower the drill RPM; the softer, the faster the drill RPM.
The larger the drill bit, the slower the RPM; the smaller, the faster the drill RPM.
For example, the other day I was drilling out a grade 8 bolt that had snapped off. I was using a 3/8" drill bit, which, to me is a "larger" size bit, since I don't have any bits bigger than 1/2". My Ingersoll Rand cordless hand drill has 2 speeds; I used the lower speed, which I think is 400 RPM. I pushed firmly forward with increasing hand pressure until the chips started coming out freely; then I maintained that hand pressure. You see, if I would have backed off on the pressure at that moment, I wouldn't have continued to apply enough force to cut the material, resulting in rubbing--not cutting & it just overheats the work & the bit. (When the chips are coming out steadily they don't have time to overheat.) If you apply too much force over & above what's necessary to produce chips, that's just as bad. I've had so much bad luck hand drilling over the years that I started a thread here on GJ recently:
http://www.garagejournal.com/forum/showthread.php?t=118351
I really got some good advice on this thread. Good luck drilling!
P.S: I even got carried away & bought a quart of Dark Cutting Oil that I spray with a spray bottle on the bit as I'm drilling, or I get a helper for that. Soluble oil is recomended, as opposed to cutting oil, but the dark cutting oil I got at Lowe's works fantastic.
E.T.A: Sorry, I didn't read the part about drilling aluminum & wood. Maybe I'm naive, but I've never worried too much about drilling these materials; they're so soft. Unless, of course, you're drilling, say, dozens & dozens of holes, which I never have to do. I think my advice applies well for steel, though.