Notice: The new and improved motor unit seen in the bottom left photo now
has standard a switch to select forward and reverse opperation.
Care must be taken when using reverse as it could be possible to
spin the threaded chuck off of the spindle.
Additionally, I have eliminated the two highest pulley ratio options as
we have found that using them will cause the motor to overheat and
they were never needed anyway, if 10,000+ rpm is desired contact
me and we can discuss additional options.
The motor manufacturer, American Bosch, specifies that with the rated 50 inch ounces of torque the motors horsepower is dependant on the rpm thus at its rated 10,000 rpm it is 1/2 hp, at 5,000 rpm it is 1/4 hp. So with the pulleys in their lowest ratio you would get 1/4 hp with a spindle speed of 1,500 rpm.
My testing found that with the lowest pulley ratio at 1,000 rpm (spindle speed) I was able to make a .250 cut in mild steel with little effort. I have no reservations as to power delivered to the work piece and have definitely satisfied myself that it is not under-powered. It starts to drop off from about 1,000 rpm and slower. The motors range is from about 500 rpm to 10,000 rpm plus the four ranges provided by the pulleys.
The four pulley ratios are:
3.33 : 1 (with motor speed of 5,000 rpm) = 1,501 (spindle rpm)
2.12 : 1 2,358
1.35 : 1 3,703
0.83 : 1 6,024