It is a torque DC drill, and is designed to stop quickly. It doesn't carry momentum with the drill. I just need to feedback inhibit the circuit between the trigger assembly and the motor and the rest takes care of itself. I'm trying two back calculate the amp/hours of the battery and the amount of time the battery has before full discharge. It's like a Ryobi drill you'd get at a hardware store in most ways. Doesn't have to stop on a dime, but quicker the better.
The carbon brush would be outside the patient and fragmentation is not a major concern because it will be inside the housing of the drill if things work out the way I think they will