Irwin Unibit Step Drill, 3/16" to 1/2"

This stepped drill will allow you to make or enlarge holes in plastic, metal, and wood safely and easily. Upgrading an imported guitar with American component brands? You'll probably need this tool or something like it to go from the metric hole sizes to the SAE hole sizes needed.

Twist drills are especially dangerous to use for enlarging holes in a body. They are fine for enlarging holes in metal and plastic parts (use a drill press if possible, and be sure the work is held securely). But they will grab a wood body and pull it from your grip almost instantly, taking chunks of wood and finish with them. A repairman's reamer works, but this Unibit is the easiest tool we've found for this task. It has a 1/4" shank and can be used with an electric hand drill. The right tool for the job.