What is this drill bit called?

[bnjp]

Originally Posted by Ned Milburn

Just wondering why you would need a reverse counter bore bit in order to drill a hole for a jack...??

Hey Ned,

I wanted it to be 1/2" on the inside and 5/16" on the outside. Just for a tighter fit on the auxilliary output. I only wanted it to protrude enough to get the nut an washer on. The strap button one is a normal hole, of course.

In other words, I wanted the jack to fit more like this since it wasn't getting a strap button. Just wanted a flush output.



I did a similar thing on a Taylor a while back but it had a custom plate to use.