Gallery, Projects and General > How do I??

Drilling small holes

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Darren:
How do I drill small holes of less than 2mm, or even 2mm for that matter.

I'm trying to make the eccentric straps for my little engine from brass.
I've snapped so many 1.5mm drill bits trying I've given up. I've tried normal cheap drills, titanium coated and cobalt and it's no go.
Mill is at highest speed of 2,000 rpm, I'm being gentle with pressure ect, peck drilling and all that.

I then tried my little drill  at 2500 rpm and still it's a no go.

So guys, what's the secret when drilling brass? There must be something I'm missing here?

NickG:
Brass does tend to snatch badly but you should still manage. I don't usually use such a high speed even with drill bits that small, when drilling brass I find it useful to nip the spindle slightly, I think it's the drill being pulled in too quickly that snaps them. Obviously keep withdrawing it after every few mm depth to clear the swarf too. Clean the drill off too if it's getting swarf stuck to it.

Can't think of any other tips and you've probably tried all of these!  :scratch:

bogstandard:
Hi Darren,

My heart really bleeds for you over this one, as unless every detail can be shown, it is very difficult to find a cure for your problem.

It is of no solace to you to know that I have no difficulty in any small drilling operations, and only yesterday I was drilling 0.8mm holes on my large mill using a big chuck and normal feed handles, drilling thru 2mm brass rod.

Is the problem when you are breaking thru or actually half way down the hole?

Because you have used a variety of drills, I don't think your problem is because your drills are too sharp (that is a normal problem when drilling brass) and is usually cured by stoning the cutting face to give zero rake.

Are you sure, because of suspect sources of materials, that you haven't got a piece of alloy in there that looks like brass, but in fact could be a bronze alloy. That would account for the drilling difficulty, as bronze can turn into a rock hard face at a moments notice, and no amount of trying will get you restarted in cutting the hole, and will give the symptoms you describe. You have to cut bronze with a continuous pressure, and by peck drilling it could have allowed the cut face to chill and become very hard.

Was the swarf produced like very fine dust (brass) or any sign of a curled swarf (more copper in the material pointing to another alloy, like phos bronze) ?

I know it is difficult to notice things like that when drilling small holes, but all clues point to maybe the reason for the problems.

Your technique is perfect for the expected brass, but it might not be the right technique for the material you have.

John

sbwhart:
Darren

John just beet me too it the only thing I could add is regarding your drill chuck is it slightly bell mouthed:- it could be holding the drill only at the back, does the drill look as if its running true. Try making a small holder for the drill in the lathe loctite the drill in then grip the holder in your drill chuck and have another go.

Stew

Darren:
Ah, I think Johns hit it here

It's got swarf and I'm getting problems when about 4-6mm in.

Now then, I paid a lot of money for this so called brass some time ago for another project. Basicly, (to give a bit of history that may or may not help) it was a full sheet of 4mm brass sheet that I paid several hundered pounds for. It was then cut up into parts on a water jet.

Am I now to find it wasn't brass at all and some sort of alloy? It looks more yellow than other brass I have.....

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