Drilling steel plate

Hi,

I'm wondering what the best way would be to drill a series of 20mm holes in thin steel sheet?

The holes are for switches, so need to be accurate.

I was thinking of using a hole punch to mark the pilot holes and then drilling with a 20m holesaw. Alternatively I could clamp it to some plywood and start off the holes in the wood?

Any tips appreciated, I don't want this to look crap!

Clamp to wood and drill through metal into wood. Wood will help hold the steel rigid while you drill.
Dot punch to mark where holes are to be, not difficult just measure twice and cut once

Stepped hole saws. There are some in Aldi at the moment, low cost and work well. You should still make sure the metal is clamped well - if it starts to spin it could gut you.eek:

Hole punch.
Drill an 8mm hole. Assemble punch over sheet. Tighten using Allen key.
Voila perfect 20mm hole. Think my punch was only 5 or 10 quid and a much better hole form than a drilled hole.

Good on both steel and allys so long as the plate ain't too thick.

Might be a bit thick for a punch? Probably about a mm. Thick enough not to bend or deform.

Specs say they'll do 16 gauge 'metal'.

I've put 3mm ally chequer plate through mine for an aeriel on the wing without problem. Just keep it lubed!

arc said:

Hole punch.
Drill an 8mm hole. Assemble punch over sheet. Tighten using Allen key.
Voila perfect 20mm hole. Think my punch was only 5 or 10 quid and a much better hole form than a drilled hole.

Good on both steel and allys so long as the plate ain't too thick.

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This is the way to get a professional finish. As said keep it oiled.

flatlander said:

Stepped hole saws. There are some in Aldi at the moment, low cost and work well. You should still make sure the metal is clamped well - if it starts to spin it could gut you.eek:

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Step drill bit for the win...

They is bloody big holes for switches, int they??

20mm is more than 3/4"

step drills is availiable in mm too, thats a smallish one, mine goes up to 25mm I think, I also have a 20mm cone drill (stepless) and a rasp bit.

step is by far the next best thing to a punch

Punches are great, but you have to buy one for each size. Slow as well, I found, as you have to drill a hole, assemble the punch through it, then make the hole. Excellent finish though.

Oldseadog said:

They is bloody big holes for switches, int they??

20mm is more than 3/4"

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They are bloody big switches!

Get a nice friend who has access to a CNC miller and get them to mill them out super accurate and ver neat
If your near oldham I'd do it for you

sp00k said:

they are bloody big switches!

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CNC water jet would be the way to go if you know somebody with one

My vote's for the Step Drills too. You can get a set of three from Amazon for very little money. They're designed to drill perfectly round holes into thin materials (but don't use them on Stainless unless you buy a £80 cobalt one - another story).