cutting holes in 3mm aluminum sheet

[sm_jamieson]

What is the best way to cut holes too big for a drill ? Aluminium sheet approc 3mm thick. TIA, Simon.

[EricP]

What sort of holes? Round, square, size?

[Ian Stirling]

There exist drills that'll do holes many meters in diameter.

Assuming you mean a mains electric drill, with a 15mm or so chuck.

How big? Is the edge finish critical? How round does it have to be?

For aluminium, it files very fast, so a quick method can be to draw out the circle required on the aluminium, then drill smaller holes with the drill you have around the inside of the line, followed up by a half-round file. This can give very accurate holes, limited only by your patience. For some things, you don't really need to clean it up beyond removing most of the sharp bits. A jigsaw is an alternative method.

[nightjar]

No hole is too large for a drill, unless you mean too large to drill through in one pass. You just drill lots of smaller holes just inside the waste area of the hole you want, join them up and file the edge smooth. Alternatively, take it to a sheet metal workshop, where they will probably use a big press to punch the hole for you in a fraction of the time.

Colin Bignell

[ben]

Scarat cutter(or tank cutters as their known) or Hole punch which use a allen key to tighten the punch as it's cutting

[sm_jamieson]

Round, about 20mm diameter. I could maybe get a drill that size. Simon.

[Grunff]

[Andrew Gabriel]

You might try a 20mm hole punch. You need to drill an 8mm hole to start with. 20mm is a standard electricians hole punch size, so it should be easy to get (can't remember where mine came from but any tool or electrical supplier will have them). You'll also need a very good quality 8mm allen key (or whatever size bolt your hole pucn takes).

I've cut 2mm steal, which was about the limit this way (had to clamp the workpiece and stand on the allen key to get the punch to cut through) Not sure how 3mm aluminium compares to that.

[Mike Harrison]

3mm may be pusing it for a hole punch, depending how sharp it is. A holesaw may be better.

[Dave Plowman (News)]

What you really need is a Q-Max punch. This gives a near perfect hole with no distortion of the sheet.

About a fiver from any decent tool shop.

[Cicero]

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[Dave]

You would end up with a three cornered hole if you used a normal drill in that thickness of metal :-)

Dave

[Nobody]

[Chip]

On Wed, 29 Jun 2005 21:20:08 +0100,it is alleged that Nobody spake thusly in uk.d-i-y:

[Chris Hodges]

How about a "cone cut" aka "step drill". Clamp the workpiece down hard though.

[John Rumm]

[nightjar]

For that diameter, I would use a No 4 Norton's fly press and a punch & die set, but I doubt most people have them available. The easiest way with a drill would be a hole saw or a step drill, both of which are readily available from electrical wholesalers; 20mm is a standard size for electrical conduit.

Colin Bignell

[Dave Plowman (News)]

Having punched many holes in electronic chassis etc, the best way by far without an expensive press is a Q-max which produces a near perfect hole. Hole saws don't, and neither do step drills. It's also difficult to keep a step drill from wandering. A Q-Max can be as accurate as your skills in positioning it.

3mm ally sheet will be fine - but keep the threads in the punch well greased.

They're about a fiver for a 20mm one.

[Ian White]

All the problems are in the early stages, when you're trying to pull the two blunt points of the punch through the metal by brute force.

So in addition to the main pilot hole, drill two more holes 180deg apart, with their edges just touching the inside of the scribed circle. Settle the points into those, and then the cutting edges of the punch will shear the rest of the hole quite comfortably.

A thin smear of moly grease on the screw threads, bearing washer and shearing edges will also help a lot.

Another dirty trick is to file flats on the head of the allen screw, grip it in the vice and turn the workpiece.

[Tony Williams]

About 25 years ago I bought a tapered cutter, tradename Conecut. It needs about a 12mm to start and will gradually widen the hole up to a maximum of 35mm. Very (very) expensive, but one of those tools you keep for years and, each time you need it, it pays it's ground rent.

When sharp it would even drill a perfect hole for a wastepipe in the side of a wooden sink unit. It was only used it in the carpenters brace, and that kept it sharp for about 15 years. Then one day (as you do) I needed something done in a hurry and used it in the 600rpm 1hp Stanley drill. :(