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Cutting tips for aluminum


NAXJA Forum User
When it comes to fabing aluminum, things are very different than steel. Rough cutting of aluminum sheets is done the easiest on a table saw. Just use a 80 tooth carbide finishing blade. Wear glasses because the chips are hot as hell. Be very careful not to have the blade up any further than necessary and make sure you have a good pusher to force it through the blade. The biggest problem I have seen is that on many cheap table saws, the rip fence does not extend all the way down to the table surface and the metal can slide under the fence with disasterous consequences when the blade grabs the sheet and shoots it back at you at Mach 3. Curves are easy using a cheap sabre saw with the fine tooth metal cutting blades. Unless its .025" or less don't even think of using hand shears.

HF has a cheap air driven sheetmetal nibbler that works pretty good, but I still have better luck with a sabre saw or a air driven panel saw. A sawzall is normally just too big and hard to handle with any precision. Electronics stores, even RadioShack normally stock a hand driven sheet metal nibbler for doing complex shapes, but it will give you carpal tunnel in a heartbeat if you try to remove too much material at one time.

Don't try and use an abrasive "metal" cutting blade. It will just load up and melt its way through the panel.

As for holes, a Uni-bit works great for cutting larger holes. A standard hole saw can be used, but be real careful to have the work piece clamped down, as they tend to stick at the worst possible time. If you are using a hand drill motor with a large hole saw, if it sticks, it can rip the drill right out of your hands and really screw up a wrist. For smaller holes, your standard brad point wood drills will give the best and cleanest holes in most cases.

The real secret is to just get it close and finish off outside radius's with a belt sander. Large inside holes can be cleaned up real nice using the cheap drum sanders on a hand drill or better yet on a drill press. An assortment of course files will also make short work of most complex hole shapes.
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A jog or sabre works for straight cuts as well - if you have something to clamp down and use as a saw guide.

It still helps - even with a metal cutting blade - to use some sort of lubrication - kerosene works well (it's also what's recommended for milling and turning.)

Don't use any sort of common grinder on aluminum - the angle grinder, grinding wheels, and a "grit wheel" for circular saws will all load up and probably fly apart on you - I'd have to check, but I think carborundum wheels can be used - but I file to shape anyhow.

The "structured tooth" carbide hole saws I mentioned elsewhere will work with aluminum - since they cut, rather than grind.

Another nice thing about the Uni-Bit step drills is that the single flute doesn't tend to chatter, and they are consistent with hole sizes and don't grab much. With patience and a little care, I understand they can be resharpened quite well - bettter than regular drill bits. It's still a good idea to centre punch with them, since they can walk if you haven't located them properly.

For any larger sections, you really want to try to use a drill press, and clamp the work to the table if at all possible - there's nothing like getting whacked with a large piece of metal to let you know you screwed up...

I forgot to mention lubrication. When cutting on the table saw, I routinely lay a bead of grease on top of the aluminum where it is going to cut. It takes a swipe of grease on each cutting pass and it slices like butter. Just watch out for the edge you end up with. If your saw is set up right, the edge of the aluminum can be as sharp as a knife. As a safety practice, I use a foot operated switch on the table saw. That way I can keep both hands firmly on the work and if it starts to bind, I can shut it down without turning loose and having it try to do a vasectomy on me.
A good trick for keeping your work lubed while using a hole saw (for any metal) is to stuff a rag saturated with lubricant into the hole saw around the center drill.

Stuff it in there tight as you don't want it falling down while your cutting.

This will only work if you are drilling downward or close to it. If you are drilling up, the lube will just puddle in the cup of the hole saw.
When I used to fab aluminum door panels, I'd just use a plunge router and carbide cutter. Be careful beading or ribbing the sheet, it takes far less pressure to tool than steel.
When using a carbide burr, or other fine toothed device....lube the cutter frequently with wax...it will keep the aluminum from sticking and fouling the teeth....
A skill saw with a carbide blade works very well on large sheets. When we get 16' sheets of diamond plate, we cut it directly on the pallet it came on so we done't have to move large sheets around. It works for any size and gets the job done. I make sure I wear a face shield, saftey glasses, and ear protection. Like stated before, that metal is hot. For a blade, we use the Diablo brand from Home Depot. They are cheap but last awhile. The larger teeth seem to work very well.
The problem with larger teeth is that they tend to catch. A good 80 tooth carbide will slice like butter. I get the cheap $14 blades from www.homier.com At the moment they have them on sale for less than $8 and they are pretty good blades. I use them for cabinet work as well. Heck at that price they are disposable.
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For detailed work on any sheet metal, the best tool I found is an Air Saw, It's a small pneumatic saw like a mini sawzall but much easier to control. Matco, Snap-On, Mac tools all carry quality air saws. The problem I found is finding blades. I can get them from the same carriers above but since I don't always have a "tool guy" coming by the house they are harder for me to get.

I worked for years in Car Audio and used this tool constantly to cut holes in doors, rear decks and firewalls. if you get a chance to pick one up I recommend it.