-
A hole saw is probably your best bet
↑This, ish. Drilling sheet that's less thick than half the drill diameter with a twist drill is pretty hard to get right even on a proper drill press. A hole saw will at least mean you're not involved in a wrestling match, although a drill press would still be a good idea.
Some screw hole punches (e.g. http://www.ebay.co.uk/itm/Screw-Hole-punch-Hole-punch-Hole-Puncher-Puncher-RUKO-12-7-63-5mm-ALL-SIZES-/401059296943) will handle 3mm aluminium and will make neater holes than a hole saw, particularly if the hole saw in question is on the end of a hand held drill. The pilot hole can be as wonky as you like, as long as the screw goes through the punch will align flat to the material.
This style of deburrer is easy to use
http://www.ebay.co.uk/itm/Neilsen-HSS-Taper-Deburring-Tool-Reamer-Pipes-10mm-34mm-Pipe-Steel-Copper-14B-/370978352112But you can deburr the holes perfectly well with a Noga with a bit of practice
http://www.ebay.co.uk/itm/NB1100-Noga-Deburring-Tool-With-2-Blades-UK-SELLER-/182366240699
You are reading a single comment by @gbj_tester and its replies.
Click here to read the full conversation.
gbj_tester
If you only want one size and fairly large, i.e. 15 mm plus . A hole saw is probably your best bet, a selection here at screwfix.
http://www.screwfix.com/p/starrett-20mm-holesaw/95906
These also work but I am not really a fan, depends what you need positional and size accuracy wise. https://www.amazon.co.uk/Q-Max-Sheet-Metal-Punch-QMA20M/dp/B0055KJGW8
Preferred for one off holes.