OK to use a spade bit to drill aluminum?
Posted 17 October 2010 - 12:49 AM
Pierre's Alt-AZ link
Posted 17 October 2010 - 03:48 AM
One of them was using a spade bit for drilling aluminum. One of our fellow ATMers did this for drilling holes on an aluminum panel, hence it was sheet metal. Even then I'd never do this since I have yet to see a spade bit that does NOT wander away (the center point usually draws a small circle instead of being centered).
If I were you I'd get a metal cutting bit (and patience & lots of lubrication with paraffin/bees wax) for the job. If you need a tight fit, then you may want to drill the hole a tad smaller and use a reamer to get to the desired diameter.
Posted 17 October 2010 - 07:36 AM
Posted 17 October 2010 - 08:52 AM
What Olivier said: a metal cutting bit (Home Depot should have it) and take your time. Probably will be easier if you drill it in steps. (Obviously make sure the piece is very securely held.)
Posted 17 October 2010 - 09:06 AM
Or, as others have suggested, buy a reduced-shank 3/4" twist bit, and drill it that way. A small (3/16 or so) guide hole will keep you on track. Still, follow my guidelines above. I think you'd be happier with the results this way........
Posted 17 October 2010 - 09:12 AM
Posted 17 October 2010 - 09:24 AM
Does anyone have a good idea of a good step interval for twist drills? I was going to start at 3/16 and go up by approximately 1/8ths using cobalt twist drills. For a nice clean finish would larger or smaller steps be needed?
Posted 17 October 2010 - 10:49 AM
I was going to start at 3/16 and go up by approximately 1/8ths using cobalt twist drills.
I've done that with good results.
Posted 17 October 2010 - 10:54 AM
Good luck with your project.
Posted 17 October 2010 - 11:24 AM
Posted 17 October 2010 - 01:08 PM
Posted 17 October 2010 - 01:23 PM
And, be sure your drill press, especially if it's a benchtop, is bolted down.
Or..... take it to a machine shop, and for a small price, you'll get a hole that's straight, square, even, and in the right place, and if you want a shaft, they'll even press it in for you. Might not cost you a whole lot more than a drill bit, either.......
Posted 17 October 2010 - 01:23 PM
I thought that I had seen some commercially bits like that in the early 80s but cannot find now. The closest that I found is a two piece design; drawing on patent available here: http://www.freepaten...com/4992009.pdf
Posted 17 October 2010 - 05:07 PM
First: buy the very cheapest spade bit, the expensive ones are too hard(material-wise) to work with. I file off the outside spikes, all you want is the center spike and uniform bevels on either side. I found for me older filed bevels worked better than new ones, the new bevels were too aggressive.
Drill a pilot hole, you'll need to drill from front and back to get a clean hole. The hole should be the same diameter as the shoulder of the spike on the spade bit. The pilot hole helps to keep the bit speed up other wise the aluminum in the hole will get too hot and bind.
Do not use cutting oil, you need the chips and ribbons to exit quickly, the oil tended to mush things up(for me)
Make sure your drill press is perfectly square, you want to cut evenly.
Clamp down your workpiece, otherwise the bit will chatter, grab the piece and make ouchies.
Go slow, feel for the cutting action. When you find the sweet spot, the cut aluminum will start to ribbon, you will feel the constant pressure and it will cut nice and smooth, the bit will cut down nice and straight.
Once I figured out the filing and drill speed, I was very impressed with how fast it went and the quality of the holes.
Posted 18 October 2010 - 12:05 AM