[JDNovak]

I know you are looking for someting simple but just to add another tested solution. . .

We interfaced a CIM to the first stage of the Dewalt by milling the CIM shaft into a hex. I believe it was done by chucking the end of the shaft in an index head and milling the exposed part. After the hex was complete the end of the shaft was cut to the insertion depth. I don't think the motor was even dissassembled.

The pinion (taken from another gearbox) was EDM'd to a mating hex. No fastener to the shaft was needed.

We put extreme pressure on the resulting gearmotor by driving the first joint of an 8' arm. The backdrive pins failed a time or two but the motor interface survived the whole season and still looked good. During the offseason we even used it to pick up chairs and stack them as a demonstration.