Good results cutting aluminum

Joe:

To the best of my knowledge, an abrasive cut-off wheel is

*not* the correct cutting tool for aluminum. The aluminum will clog the cut-off wheel and you will have to redress the wheel or replace it. Instead, you want a carbide blade with as many teeth as you can swing. The more teeth the better. The abrasive cut-off wheel is exactly the correct tool for cutting *steel*.

Hmmm $18. I may have to make a trip over to Harbor Freight myself. ;-)

-Wayne

Joe Strout wrote:

When I work with aluminum, I make a rough cut with a fine tooth bandsaw, leaving about 0.05" of slack. Then I finish it with an endmill, using a climbing cut on the first pass, and a higher speed desending cut on the final pass. This gives a very accurate cut (+/- 0.001") and a mirror smooth finish.

I am not sure anyone else has mentioned it but...

If your hacksaw will not cut aluminium, something is badly wrong. You do have the blade the right way round don't you? It should cut on the forward stroke. Sorry if that is insultingly obvious.

Pete

It's not obvious -- in fact it's not clear to me why it should matter. If I had it the other way, it would simply cut on the back stroke, right? But in my hands, it didn't seem to be cutting on either one. (Or perhaps it was, but well below my patience threshold.)

However, I'm inclined not to worry about it, since the cutoff wheel is working beautifully. (I will keep in mind Gordon's warnings, however.)

Best,

- Joe

Oops -- I meant Wayne's warnings. Sorry about that, Wayne!

Best,

- Joe

The natural action when cutting is to put downward pressure on the forward stroke and lift up on the reverse stroke.

You may like to have a look at this:

Pete

Thanks, that's a very helpful reference. Based on this, I'd guess that the problem might have been the wrong blade; this aluminum is only 1/16" thick, and I don't think two teeth of this blade would fit on it at once

-- I haven't counted, but I'd guess it's closer to the 14 teeth/inch than the 24/inch recommended for angle iron (or, presumably, angle aluminum).

Best,

- Joe

I have heard of abrasive wheels made specifically for aluminum cutting that will not gum up like the steel cutting wheels. I have not seen one personally though. If the wheel gums up, it's worth looking for.

Good Luck, Bob

No sweat.

If any documentation came with your abrasive cut off wheel, look to see what materials it is approved for.

Back when I was taking metal shop in the early 70's in high school, the metal shop teacher would really hassle anybody that put aluminum on the grinding wheel. It was easy to tell when the grinding wheel was gummed up with aluminum.

It is possible that there have been technological improvements that have made aluminum abrasive cut off wheel feasible. Carbide blades work great tho'.

Enjoy,

-Wayne

Good hacksaw blades will have an arrow the shows which end goes at the front of the tool. There is more cutting pressure, and therefore results, when you push a saw rather than pull it. That means you want the teeth pointing away from you, or the front of the tool.

The biggest problem with using any power tool for cutting channel stock is that you MUST use a clamp to hold down the free ends. Otherwise, do it often enough, and eventually you'll have a piece of aluminum hurling toward you, your car, a pet, or a loved one. I had this happen once, and I calculated the metal flung out at around 50 mph. It hurt like hell and seriously bruised my hand.

-- Gordon

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

Nothing that came with the wheel or the cut-off saw lists any materials. I'm calling Harbor Freight's "for technical questions" line, so we'll see if they have a clue. (So far they don't, but I'm being transferred to "the technical department" as we speak.)

I'm hoping I'll be able to tell when it starts to get to that state. So far, after making 5-10 cuts, I can't see any change in the wheel. If it does get gummed up eventually, I'd be inclined to just replace it -- they're less than a buck each, so I'd have to go through a LOT of them to bring me up to the cost of a power miter saw.

No doubt -- but that'd be a different tool, I think (i.e. not just a disc change). One I will probably spring for eventually, but I'll take my $18 chop saw as far as I safely can first.

Best,

- Joe

Well, frick. I did finally get somebody at Harbor Freight who sounded like he knew what he was talking about, and he said that using it (or any grinding wheel) on aluminum was a very bad idea -- the aluminum might expand during cutting, grab the wheel, and cause it to fraction into lots of pieces. He recommends this tool only for cutting steel.

And yes, this is what you all have been telling me all along. :)

He said that for aluminum a hacksaw or bandsaw is the right tool; I presume from what I've read elsewhere that a power miter saw, with the right sort of blade and some lubricant, would also be safe. But I haven't got one of those, so maybe I'll turn my hacksaw blade around the right way and give it another try.

Fortunately, I'm still well within my 90-day return period... so now I just have to decide whether to take it back, or keep it and figure I got a great deal on a steel cutter. Can't imagine why I'd be cutting steel though -- it's too heavy for most bots, and I can't drill it (not with my current tools, anyway). So this would probably just end up sitting on a shelf.

Rats! But, at least my education is ongoing, and I didn't sustain any injury in the process, so I guess in that sense I'm doing well. :)

Thanks,

- Joe

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.

But you ask so politely, and you actually listen to the answers. Everybody benefits from the dialog.

If you can find a 6" carbide blade that fits your chop saw, it should cut aluminum just fine. Doing a Google search for 6" circular saw blade carbide returns multiple hits. You want as many teeth as possible. The only issue is what size hole is in the middle of the blade.

While I'm talking about it. Cutting aluminum with circular blade is *noisy*. You definitely want some ear protection -- either ear plugs or ear muffs.

Of course, eye protection is an absolute must. Don't even consider turning the saw on without adequate eye protection.

Lastly, the resulting aluminum flakes are messy. Don't run the saw in the middle of your living room. ;-)

I'd recommend keeping the chop saw if you can find the carbide blade.

Personally, I've benefited greatly from this discussion. I hadn't realized that my knowledge of hacksaws (and grinders) was so lacking. This explains some of my frustrations in the past dealing with these tools.

Thank you to both the original poster, and those who followed up on it.

Joe Dunfee

I'll mention here that rec.crafts.metalworking is also a group filled with many knowledgeable people, who are very quick to help as well (on the downside, it tends to have too much off-topic politics, and of late it's been hit as hard by the sporge and mi5victim floods as this one).

Harbor Freight sells a basic handheld bandsaw that has worked very well for me in cutting off steel and aluminum. If you watch carefully, it comes up for sale at about $60 once or twice a year. The blade that came with mine is still going even though I bought a package of Milwaukee brand blades (they're the same size for the ~$300 Milwaukee handheld bandsaw and the HF unit).

Pete

Depends on the cutoff disc, but some are made to work with non-ferrous metals as long as the metal isn't too thick. The advantage is that they're cheap. If you want the absolute proper cutoff saw for a power saw you'll want to get a blade for non-ferrous metals, but these things are often more expensive than the tool you're putting them in.

Unless you're doing production work, or have a ton of material to cut, you really don't need it just to cut aluminum extrusion. A hack saw with a good miter box does the trick. Just buy a pack of good blades and let the tool do most of the work.

-- Gordon