[Milsurplus] "N" bulkhead punch?

[Glen Zook via Milsurplus]

The punch is often called a "D" punch and, in the "goode olde dayes", very common.
There are different sized Type "N" jacks.  However, at least those of which I generally run into, those are 5/8ths inch in diameter. Glen, K9STH

Website: http://k9sth.net
      From: W2HX <w2hx at w2hx.com>
 To: "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net> 
 Sent: Friday, December 19, 2014 5:46 PM
 Subject: [Milsurplus] "N" bulkhead punch?
   
Hi friends,

I am building an outdoor antenna control enclosure and I've decided to use "N" bulkhead connectors to bring RF in and out of the enclosure (no need to debate the benefits/disadvantages of "N" vs "SO-239" connectors)

Most of these bulkhead connectors have a "flat" side. This flat side prevents the otherwise round connector from twisting when tightening on a cable.  I don't have any special tools to make this type of a hole in my enclosure. I am guessing that a metal punch (like a greelee) should be used to make such a hole.  Does anyone know what kind/model of punch I should look out for? What size?