Thought this might be more germane to warmwater flies, and most of you are probably already well aware of this, but Harbor Freight now sells a 6 piece hollow punch set with ?? hex drive to fit your drill.

Hex shanks for secure, non-slip fit in any chuck
Sizes: 3/16", 1/4", 5/16", 3/8", 7/16", 1/2"
Overall length: 2-3/4"

HF Punches.jpg