In my opinion , when the load gets really light, the speed really slow, the duration of use highly temporary, nothing will provide the motor and gearing required like a cordless drill motor, meaning a cordless drill, complete. Old guys call them drill motors instead of drills because drills are the little twisty things that actually make the holes
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Those drill motors are cheap, powerful, geared real slow, have a "throttle control", can be clamped onto the machine several different ways. The chuck will clasp a rod with a sprocket on it, at least for a while, and when that one starts slipping you can replace it with a "real" chuck that tightens with a key.
The only downsides to using them is not much speed nor power, plus nobody learns much of anything about electricity. If neither of those things bother you much, well, I guess it is off to harbor freight! …..Joe