On Wed, 26 May 2010 09:03:20 -0600, Lewis Hartswick
wrote:

DoN. Nichols wrote:
Be careful not to use a Greenlee knockout punch, because the
diameters don't match the names there -- they match the conduits for
which the knockouts are used.

Good Luck,
DoN.
Use a " Chassis " punch they are as marked.
...lew...

Yup. They don't tend to be rated for SS but I doubt one hole is going
to wreck them. Should cost about $40 new.

http://www.toolup.com/greenlee/730bb-3/4.html

(you have to drill a pilot hole for the bolt first)


Or a step drill:

http://www.mcmaster.com/#8841a23/=79atvx