Drilling Aluminium

[.....]

A quick question for you all.

I've got a plate of aluminium (I think) 3mm thick that I need to drill 3 4mm holes in.

Right I take it I'll need a 4mm HSS (Hardened Speed Steel) drill bit? Is this OK to be done with a normal hand drill considering I don't have a clamp of any sort to hold it? I'll probably just hang it over the edge of something and get someone to stand on it or something. Is this OK or is it going to go pear shaped?

[gavin]

probably more claret coloured than pear shaped, when the drill jams in the ally and spins it round slashing whatever is in the way......


ally is soft, but dont be fooled into thinking you can get away with not clamping it somehow.

you need to rig some kind of clamp to be safe -even if it is just a great big bit of wood with some woodscrews driven in around the ally plate to stop it moving!

[tatters]

Just get some one to stand on it, drill bit is ok but use a punch to indent the point you want to drill on to stop the drill bit going off center.
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[Bezzer]

By hand drill I take it you mean an electric one?? it's going to spin as you break through the far side. Alloy is soft so it clogs up a bit and can have a fair whack as it twists. It's much safer and you will get a cleaner hole if you can use a g clamp or even mole grips(with some protection so you don't mark the alloy) as it's only thin to clamp it to something solid.
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I used to be indecisive but now I'm not quite so sure.

[Cillit-BANG]

Depends on how big the piece is. If you can get your boot on it then you'll be ok. Don't hold it by hand because when it catches it will hurt.

You may be better off with 2.5-3mm pilot hole first then 4mm to finish.

[stinkwheel]

Centre punch the holes, bung it on a block of wood, stand on it and drill using a SLOW drill. Be prepared for the drill to bite but remember if you are going slowly and have a good hold of it, things shouldn't get out of hand.

The trick with drilling metal is to go as slowly as possible, then you can feel it bite and back off a bit. Drilling slowly also means you don't knacker your drill bits by overheating them. You'll know you are going at the right speed because there will be spirals of swarf coming off as opposed to chips of flying metal. With aluminium, I usually go almost all of the way through then flip it over and finish the hole from the other side, makes a neater hole.

If you're worried, use a hand drill. A good sharp bit will suck itself into the metal.

You shouldn't really need pilot holes for 4mm but they wont do any harm.

[Nath]