On Thu, 28 Aug 2003 20:21:50 +0000 (UTC), "Dave"
wrote:

I have just tried drilling some 3mm thick mild steel with a 13mm
hole......... hell of a lot of noise, loads of vibration and now the drill
seems to do anything but drill!

You're pretty lucky it didn't decide to spin the metal, rip a hole in
your leg and leave you bleeding to death from a femoral artery ! 8-)

13mm isn't a small hole in thin steel. Now I'm a cowboy, but even I
don't like to drill that with a handheld drill. If I have to, I do
make sure it's clamped down pretty well. If I don't have a slow power
drill, I'll do it by hand. I am _not_ going to over-speed a big drill
bit into something that's likely to fly up and tear chunks out of me -
Sorry, done that one far too many times already.


Use lubricant. Something oily is good. Buy some RTD if you want (it's
gooey enough not to run away from a hole in a wall), but old engine
oil is a lot better than nothing.

Drill a pilot hole. You should be able to fit the centre chisel edge
of the bigger drill into the existing pilot hole.

Use a backer - bit of scrap wood clamped on the back, or something. If
you don't do this, then it's going to go completely random when you
break through,

Go slow. For 13mm, go damned slow.

Use decent drills. The shed sets are garbage. Go to a real engineer
and get some black ones (you're in the UK - buy some Presto), not the
Chinese gold-coloured TiN ones.

Don't drill 13mm holes in thin sheet with a handheld twist drill. Get
a Conecut or something if you're going to make a habit of it. A
two-flute drill that isn't held rigidly gives you a lousy hole that's
probably more pentagonal than round.