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lost eden 17th January 2012 08:37 PM

Drilling ~1mm thick steel case metal
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I've just bought a nice big 3U rackmount case to mount a pair of LM3886 monoblocks in & I need advice in how to make some holes in the case for sockets/switches/etc.

As far as I can tell the metal is 1mm thick steel. I have a set of 'high speed steel twist' drillbits & an old 350W 3100rpm power drill. This combination worked nicely for drilling the thick aluminium you see in the picture but I'm not certain how well it will work against steel, particularly so thin. Do I stand a chance or will the drill completely mess up the enclosure?

I also have a Dremel, which can't take thick enough bits but probably runs slower than 3100rpm at its lowest setting so might be useful for making pilot holes?

Any advice? I don't want to mess up a case I just spent 65 on...

vacuphile 17th January 2012 08:47 PM

Can't you find someone with a drill press to do it for you, for some small fee? Free hand drilling gets messy easily, even with the right equipment and experience.


lost eden 17th January 2012 08:50 PM

I asked around for anywhere with a drill press when I was drilling the aluminium & I couldn't find anywhere unfortunately.

M Gregg 17th January 2012 08:55 PM

If you must drill by hand,

Make sure you measure twice centre punch and drill once..

Also put a very small drill through first #3mm this helps to keep it on centre..

Also you can use masking tape to cover the case and mark out on that plus all other work and then remove..

M. Gregg

M Gregg 17th January 2012 09:02 PM

This might sound strange,

I find standing above it helps use your feet to hold you are drilling into a thick catalogue is better than it twisting in a vice..That said if you have a workmate that helps..

Large holes you can clamp it to scrap wood and drill the wood gives support..and your cutter will go through it!

Also probably assemble it mark out then strip it and drill..if it twists as you drill it can run off..
Variable speed drill helps..something with just one speed is a pain and will scrap your project..and burn cutters out (slow and steady)
I have done wonders with the budget argos 12.00 drill variable speed..
More about finesse not brute force..

M. Gregg

M Gregg 17th January 2012 09:13 PM

Sorry waffling on.. :)

PS use cutting lube with steel and hole cutters..

M. Gregg

nigelwright7557 17th January 2012 09:47 PM

I tend towards switches jack plugs etc that require round holes then buy sheet metal punches. This is will give a good finish without any sharp edges.

Buckapound 17th January 2012 09:58 PM

Large diameter twist drills have a tendency to either distort or rip the metal if it's too thin, and can also make funny, lobe-shaped holes when freehand drilling without a press. When using them, it's advisable to clamp the metal between a couple of blocks of wood for support. On chassis', not always practical.

A step drill is probably the best tool for drilling large holes in sheet metal, but they're expensive.

Up to about 6mm or somewhat larger, you should have no problem. I used to use a handheld taper reamer, which is a little bit of a pain, but they work just fine. Cheap, too, and should be pretty available.

With a Dremel, you have the option of drilling a series of small holes near the perimeter of the hole you're making, then cleaning the edges up with the Dremel. Get a small carbide burr (rotary file), and you'll be amazed by how much metal it can move. If you have holes larger than10 mm, this is the method I'd use with simple tools.

Of course, it's not exactly the tool for the job, but if you just have a few holes to drill then it's not worth spending a lot of money for more specialized tools.

M.Gregg was right on the drilling; keep the speed low and use some kind of lube, and keep some pressure on it. You don't want the bit spinning without cutting. Make sure your drills are sharp, too.


M Gregg 17th January 2012 10:00 PM


Originally Posted by nigelwright7557 (
I tend towards switches jack plugs etc that require round holes then buy sheet metal punches. This is will give a good finish without any sharp edges.

I agree,

trouble is if its just one project it can get be expensive..Then again cutters (hole saw) are not cheap..

I would not try to cut more than 30mm by hand drill..:)

Yes how to drill a square hole with a round drill easy...LOL try 10mm in sheet metal...with no pilot hole even easier..

M. Gregg

chrisb 17th January 2012 10:04 PM

If the panel is removable, clamp on work bench with sacrificial scrap of wood and several padded clamps - this'll free up both hands to control the drill, as well as reduce nasty edges on rear side of cut out areas. Cut undersize and finish off with fine cut files - cheap sets are available with small profiles that can allow for more than simple round holes - I consider them to be essentially disposable.

sorta duplicate of buckapound's post

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