Good results cutting aluminum



Got it, thanks. I did indeed have the blade in backwards.

More good advice, though my natural sense of caution (sounds better than "cowardice") had already led me to this conclusion. One end is held by the cut-off saw, but the other end I always hold down with a C-clamp.
I did more work over the weekend, cutting quite a few pieces, sanding off the rough edges with a Dremel, and then drilling. All went reasonably well; drilling aluminum really is as easy as everyone says, which was a nice surprise. Drilling exactly where I meant to drill is harder, though; the bit tends to wander a bit before biting down, despite my efforts at holding it steady. I think a small drill press may have to go on my birthday list.
Best, - Joe
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There is a small, cheap hand tool called a centerpunch: it's a pointed piece of hardened steel. You put the point where you want the hole to go and hit the end with a hammer, creating a dimple in the aluminum -- this serves to locate the drill bit, and keep it from walking. With aluminum as thin as you're talking about, you'll want the work piece resting on a wooden board when you use the centerpunch. For larger holes, you can use the centerpunch to make a dimple, then drill a small pilot hole, then drill your full-size hole.
In a pinch, a nail works as a poor centerpunch, especially in really thin aluminum.
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Joe Strout wrote:

The trick is that you use a center punch to mark the hole position and guide the drill. This works great in aluminum.
If you want a drill press, don't get the "Dremel tool drill press"; it's total crap. Get a small bench-top drill press. Take a look at Grizzly G7942, (http://www.grizzly.com/products/G7942), a mini drill press for $85. Get the drill press vise ($10.95) to go with it. For about $125, if you have the room, you can get a low-end but full size drill press. This is enough for soft aluminum; if you're drilling steel, you need a heavier duty drill press.
The next step up is an X-Y table for a drill press. Then you can put holes in the right place consistently. Grizzly Industrial used to have a low-precision one for about $100, but they seem to have discontinued it. We had one of those at Team Overbot, on a low-end drill press. Very convenient. We had to make many mounting brackets, and used 1/8" x 1" steel bar stock, a bender, and a drill press for most of them.
Beyond that, you're into machining for the sake of machining. I know three people who have full-sized milling machines at home, but they don't use them enough to justify owning the beasts.
There's also "emachineshop.com". Download their program, design the part, pick the material, get an estimate on line, put in a credit card number, select number of copies desired, and start the job. Their free CAD program is quite impressive, and it understands their manufacturing capabilities. It won't let you submit a design they can't make, and it knows when you're doing something dumb, like specifying a square inside corner on a milled part.
                    John Nagle
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Missed this comment before: when working with power tools, I have no idea what the word "cowardice" means. My father did (well, at least he had a concept of "safe enough"), and he had nine fingers for the last few decades of his life due to a disagreement with a table saw.
"Ah, I just thought of a way to make that process safer" is a phrase I'm very familiar with, and one I try to think of ways to employ *before* I'm holding what's left of my hand since what I last did wasn't quite safe enough. So far, so good...
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Excellent points. Thanks for making them.
This is part of what bugs me about combat robotics. To play in that sport, not only do you have to work with some pretty serious power tools (cutting steel and so on), but you're also purposely building a very destructive weapon. Unlike most power tools, it is *designed* to be destructive, and moreover wasn't designed by a professional, experienced engineer. And how many participants have a thick Lexan arena to test it in? I suspect most of them are just tested in the garage or driveway, following procedures that their builders hope are safe enough.
I want my son to grow up knowing how to build and fix things, and excited about science and engineering. But I also want him to grow up with all of his fingers and senses...
Best, - Joe
--
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Learn more and discuss via: <http://www.strout.net/info/science/polywell/>
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