On 2008-12-22, K Ludger wrote:

[ ... ]

Wow so many replies - thanks to all!

I'm leaning toward drilling a single hole then using a Green Lee or Bramley
punch (wrench driven unfortunately).

Ouch! Get the ball-bearing screw for it, which will reduce the
required torque somewhat -- and use high pressure grease on the threads.
It is still going to be a lot of work going through matierial that
thick. (Hmm ... was it steel, or aluminum?) Steel will be stressing the
Greenlee punch nearly 1mm thick material. Aluminum you can probably do.

Put the punch on the outside, and the die on the inside, and
hold the punch in a heavy vise. (Or, I guess that you could get an
open-end wrench to fit the distance between flats on the punch side of
things.) Anyway -- the die goes on the inside because it will scuff the
surface of the panel, so put it where it can't be seen.

My drill press while substantial has been retrofitted with a 1/2 hp single
phase 240V motor and with the current chuck (not morse taper) would not
handle a rotabroach.

The chuck itself would not be Morse taper anyway. It might have
a female Jacobs taper in the back of the chuck to adapt it to a Morse
taper arbor -- or directly to the spindle if it is a cheap or small
drill press. Or -- the spindle might be threaded, and the chuck screwed
onto that.

The enclosures are an off the shelf prefabbed item my
customer uses regularly. They are around 1'x1'x1' and are difficult to
clamp/locate on the drill press. The hole location is not critical within
0.1" will be ok, its for a cable gland to be fitted into.

O.K. What about the diameter? You were mentioning either 1" or
25mm in the "Subject: " header, and they are not identical. 1" is
25.4mm, so is a difference of 0.4mm enough to be a problem for whatever
is going in the holes?

On the topic of chassis punches, will a 1/2 drive air wrench similar to the
one at the link below drive a Green Lee or Bramley 1" punch?

http://www.toolstation.com/images/li...bbig/45203.jpg

I doubt it. Those are good for quick screwing and unscrewing of
bolts before they tighten up, but they stall before you get to the
torque you need for the Greenlee punch. (At least, the one which I have
would.) You could use it for taking up the threads (those drive screws
are *long*, and for backing the screw back out, but you'll have to shift
to something manual for the serious part of the work. I would probably
use a ratchet torque wrench (if it is within the range of the torque
wrench's capacity) because it has a longer arm than the typical ratchet
wrench.

This probably means that you will want two sockets to fit the
Greenlee drive screw -- one for the air wrench, and one for the torque
wrench.

Would using soap / beeswax aid the punching operation?

What workpiece material? There is a wax designed to help
cutting with a bandsaw (Castrol makes at least one version of it), and
it might help with the aluminum if applied to the cutting edges of the
punch -- but you want a good high pressure oil or grease on the threads
of the drive screw.

At least with the punch side on the o8utside, you can grip the
punch's flats with a good heavy bench vise (and you'll need a *heavy*
bench too if you are doing steel of that thickness).

Good Luck,
DoN.

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