Tools, Sharpening and Power Machinery - Drilling and cutting aluminum flat bar?

I have a 3/4" thick aluminum flat bar 4" wide. I need to drill a hole in the center w/ a diameter of 3 1/4". Can someone please suggest a drill bit to do this in aluminum?

Also, what is the best blade to put in a miter saw to cut aluminum at 3/4" thick?

Thanks for the suggestions...

You may be able to find a large diameter hole saw to cut the hole. I would use a jigsaw with a metal blade to cut it to length. Good luck.

dsfii,

Majak is right about the hole saw.
A good quality one, preferably with finer teeth than one for wood but a wood cutting saw will work.
You can purchase a blade for your mitre saw for cutting non-ferous metals.
Don't subscribe to the "backwards blade" myth. It's a very dangerous thing to do.

When using a hole saw you have to only use a moderate speed and be on guard for grabbing and overheating.
A lubricant will keep the blade and material cool.
Same goes for slow and light pressure but a firm grip on the handle of the mitre saw.

how precise does it need to be ?

A hole saw that big is going to be expensive I would

either

draw the circle and then drill the edges with a seris of 1/4 " or so holes then knock it out and smooth it up with a file

or

cut it with a jigsaw

either way would be cheaper , about the same effort , just not as precise .

A hole saw is probably your simplist way to make the hole. Keep the blade cool with lubricant. I hope you have a drill press because a hand held drill won't work as well. I don't even know if a small hand-held drill motor would be able to to the job. If you all ready have a hole saw mandrel , I would guess that a the 3-1/2" blade would cost around 15.00

Most of the big names in professional miter saw blades make blades to cut aluminum (Amana, FS Tool, CMT). Professional aluminium blades are expensive (70.00-120.00 for a 10"; Freud might have something less expensive). These blades typically have a triple chip grind with a negative hook angle. If you go this route, the place that sells the blade should also carry a stick lube (wax type lube) that should be put on the blade.

You might want to call a machine shop or fabrication shop or welding shop and see what there prices are to do the work. If you just have one or two, it might be cheaper than the blade. Miter saws aren't aren't my favorite tool to cut that thick of aluminium. I have a love hate relationship with holesaws.

using one of those abrasive disc blades like they use on metal shop chop saws and on concrete saws? I believe they are about 4 or 5 bucks. I believe they fit fine-just press gently--don't force it be patient or you'll burn up your saw motor. I'd just use my4.5" right angle grinder with a cut off disk-yeah you'll have to use your "sharpie" to trace the angle you want first. I also see an "aluminum/laminate" blade in my craftsman catalog (tho that might be for sheet and I think you're talking "plate" thickness). I don't know about your local stores but I see my local "tractor supply company" has a 10piece cobalt drill bit set "for stainless steel" for 16.99 it comes with up to a 1/4" bit--that will get you a starter hole then use the jigsaw with a metal blade and lastly smooth the hole with a die grinder.
And I can't stress enough--you burn out something (eventually) if you don't use a lube.

Tim

I would suggest a carbide tipped holesaw. Not too expensive, but still around $50 US for a 3.25 inch size. Last time I tried smaller holes in aluminum, it was a disaster because the aluminum gummed up the teeth on the standard holesaw. I was probably trying to cut too fast, also.

I watched some glass wall installers set very thick aluminum channel (about 4 inches high and 2.5 inches thick, solid except for a 3/4 inch groove for the glass) and they used a miter saw to cut it. Didn't look too closely at the blade, but it had plenty of carbide teeth.

Might not be a bad idea to contact a local machinist.

I would suggest a carbide tipped holesaw. Not too expensive, but still around $50 US for a 3.25 inch size.

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Might not be a bad idea to contact a local machinist.

Yes. You should be able to find a local machinist who will do this for under $50.