What material ? Are these standard rack mount panels ? Standard Rackmount screw is a 5/8" - 3/4" 10-32 screw. I've seen everything from Modified truss-head, to Oval head with counter-sink washers, as far as style of screw goes.
Oh wait looking back at your post now. You mean the screws for mounting the connector
itself. I've almost always used Rivets for mounting sockets like that. However there are drawbacks to using rivets, like having to drill them out to remove them. If you use rivets besure to get it perfect, as a half a--ed job of riveting will always bite you in the end. The "D" Series Connectors are tapped and counter sunk to accept a standard M3 Bolt
which roughly translates to a #4 machine screw
. Basically a 3 mm bolt
with a counter sunk, or oval head. Here's a great link http://www.marfas.com/machinescrewtapping.shtml
It has Tap, Drill, thread count etc
. for most common American screws. For the Nuetrik you just need to translate the 3mm hole size, unfortunately it's like a #4.5.
If you don't have it yet here's a cut out and dimension diagram for the standard Nuetrik series. Print it and used it as a template
(< who knew a Carp would know all this silly stuff about sound gear? > < Ok I used to build cases.)