12V drill motor? I'm guess that's a Mabuchi 550 style of motor. 95W at 15000rpm and no load speed of 17500rpm.
My calculations say a 95W motor would swing an axe that big in 0.30 seconds, which is an average of 99rpm. That would need a 150:1 gear ratio to be efficient. A smaller gear ratio wouldn't let the motor spin up to its peak power band and it'll just draw too much current and make everything hot.
A big scooter motor is efficient with a 8:1 ratio, which is why I prefer to use them. And the lower gear ratio counters the extra weight of the motor.