A counter sink is normally used to sink screws flush with the surface of your work project. Essentially though it is just a blade at a 45 degree angle, and it will take the burrs off of any hole that it fits in. I use this for quick cleanup of all the holes that I drill in kydex, before putting rivets, eyelets or other hardware in.

I'll admit, I still haven't found a way of drilling through kydex without ending up with the burrs, and sometimes spinning the work piece, email me if you have any suggestions!

You can find them at sears, at the following link click here