09-24-2018, 08:45 AM
An electric sewing machine motor is an interesting idea. I used a sewing machine motor and speed controller to build a fishing line spooler once. The variable speed is controlled with a foot pedal and works great for the spooler but might have to be modified for a belt grinder. Of course the variable speed controller is built in and comes with the motor. The question is simply whether or not a motor can be found that has enough uumph to sharpen a knife. Maybe the one linked in your post Ken does. A Harbor Freight 1 x 30 is a 1/3 HP and barely gets the job done so maybe 3/4 HP will do a pretty good job.