Just to say thanks for all the help.....
I got a new drill with variable speed, a Champion 750W from Focus, a new B&D
Bullet drill and used some cheap engine oil i had laying around as lub.
Decided that although in theory the drill had a 2 speed range setting that
the slowest was still too fast for the 12mm drill bit, so I held the
trigger, pushed the drill down fairly hard and drilled pretty slow, while my
helper sqirted oil on the work. What a difference! It was amazing...... cut
though the steel easy :)
Thanks again
Dave
PS
The work was clamped in a vice under a wolfcraft drill stand, which was
clamped to a B&D workmate. All seemed pretty solid and safe'ish!
I've got the tee shirt for that, but it was a long time ago :-)
I've drilled many metals since then and have learned a lot about the
subject.
I'm not sure about the quality of that drill, but see later.
a
The maximum speed you quote is for best conditions. 1000 RPM is a bit fast
for the average home user.
Does
Some one else has said that you should pilot hole the metal by using a
smaller drill, followed by a larger one. Good advice.
When you come to drill the hole to the size you want, you will need a much
slower drill rotation speed. The only way to do this, is to start and then
stop the power to the drill, thus keeping the rotation speed down. This will
be hard on the power tool, but kind on the twist drill. If the power tool
heats up, take a break till it cools down.
By keeping a heavy pressure all the time, on the drill, (very important you
keep lots of pressure while cutting the hole) on the power drill, to ensure
that you continue cutting, you will be better off starting and stopping the
drill by flicking the switch on every few moments. This keeps the rotational
speed down and will prevent the cutting edge of the drill from blunting
through heat.
HTH
And I hope you understand what I am saying :-)
Dave
Dave
I agree that this is the best way, provided your drill motor has enough
power to do it. The problem comes when you don't have enough power
to let you push hard enough to get a sufficient bite. Then the bit just
spins and dulls. A clue you aren't pushing hard enough is when you
don't get nice curls coming off the bit as you drill. If you're just getting
piddly little shavings, you aren't feeding aggressively enough, and the
bit dulls prematurely. If the motor stalls when you push hard enough,
you don't have enough motor (or it's geared too high) to let you drill
that hole.
Gary
A lot depends on the hole size, and the rigidity of your drill press /
hand drill.
If you try to drill 13mm straight off with a hand drill, then there's
the potential for so a slight difference in cut depth from side to
side turning into a considerable off-axis force. The hole is likely to
wander like crazy, possibly with injury.
If you're drilling on a rigid drill press, then even then you can have
problems with thin sheet (and I mean <16 gauge) deforming beneath the
drill bit.
Personally I like to use a stepped drill or similar for this sort of
work (HVAC ?) You not only drill a pilot hole, you use it to guide
the next drill step.
On 30 Aug 2003 07:56:21 -0700, snipped-for-privacy@cbpu.com (JohnM) wrote:
What are you drilling these holes with? Bench drill or what? I'm not an expert
but make sure you lubricate the bit, use even pressure, drill a pilot hole(!),
use a properly sharpened or new bit, keep the revs down. It *is* mild steel you
are drilling isn't it? Sure? Maybe try working up to that size using smaller
bits.
buy a pillar drill. Get some good quality metal drills, I bought a set from
machine mart for about £30, sizes from 1mm to 13mm. Skimping on equipment
will get you nowhere.
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