This Instructable will cover the process of how to modify a generic cordless drill for use in robotic applications by removing the chuck and disengaging the slip clutch. It will also cover mounting options for the motors.
Why use a drill motor instead of a purpose built gearbox/motor like a Banebots P60
1. Cost. It's around $80 for a banebots gearbox/motor and about $30 or less for a cheap drill.
2. Drills are designed to be lightweight, durable and powerful. (isn't that we want in a motor?)
3. They are almost the same thing as a Banebots P60, but with more plastic. they have a similar final output speed*, and identical motors in most cases.
4. You get a battery and charger, which are always useful.
I use two of these in my top ranked combat robot Phoenix
* Banebots 26:1 gearbox with a 550 size motor outputs ~900rpm, which is about the same speed that most cheap drills spin at.