okay so i have been sort of holding my tongue on this one hoping that the
thread would die but it hasn't so here i go for better or worse.  if you
want to make a 2" hole with a greenlee or similar punch you are going to
need a 7/8" or so hole saw.  you need a hole saw so that you can fit the
threaded shaft of the punch through the sheet metal.  additionally you
need a hole saw bigger than the root diameter of the threaded punch shaft
because as you punch your hole the slug will deform and if your shaft hole
is too small the slug will get stuck on the threaded shaft.

when making most conduit hole i don't use greenlee punches but expensive
hole saws.  normal hole saws are bimetal blades.  the bimetal tooth
structure is what makes the hole saws chatter and leaves that ruff hole
that looks and feels like it will cut your fingers up.  that said i tend
to use hole cutters made by the following companies.  they were both
started by the same guy so some of the products show up in both catalogs.
note to gary if you put these in a mill the holes are to die for pretty
:).

http://www.blairequipment.com/

http://www.hougen.com/

these hole cutters are expensive but if you oil them when you cut with
them and generally take care of your tools the will last you a lifetime.
they can even be resharpened when they get dull if you want.  i probably
get 200 holes or so out of my 7/8" cutter before it gets damaged, usually
from being dropped.  these things even cut beautiful holes with one or
two teeth broken off.

jonathan

On Sat, 22 Jan 2005, Gary Lee, Vanagon Racks wrote:

> >Plasma torch also would work very excellently if you have the grand to buy
> >one.
>
> I wish they were that cheap :)  I have one that cuts up to 1" thick. It
> makes heat and smoke and the plasma stream is torch-flame like.
> I have a choice, and I choose to use a holesaw for making that particular
> hole in the van floor.
>
> I notch hundreds of pieces of metal tubing with holesaws.
> In my experience, bi-metal hole saws are all pretty much equivalent in
> quality and ease of cutting.
> Even if you wanted to buy a really good one for lots of money, it wouldn't
> work much better than a cheaper one.
> I used to buy lenox holesaws at about $10 each.  They don't last any longer
> than the $6 no-name bimetal saw.  The lenox are ground and are a little more
> accurate and are centered a bit better however.
> Like I said before, the teeth tear off before they get dull.  And when it is
> that the teeth accidentally tear off, you can never know.
>
> Gary Lee
> http://www.telusplanet.net/public/gary2a/vw.htm
>
>
>