The standard Sherline pulley set is geared to turn the spindle at a maximum speed of 2800 RPM. This offers a speed range sufficient for most lathe and mill operations while taking maximum advantage of the motor's torque. There is a second pulley range that reduces top speed further while increasing torque even more for turning large parts or running slow cutter speeds.
However, we often get requests for higher turning speeds from people running small diameter cutters for jobs like engraving. For this purpose we have developed a pulley set that is capable of turning the spindle at speeds up to 10,000 RPM. Naturally, when geared to turn such a high speed, power is somewhat reduced, but this is not normally a problem with small cutters or when turning small shafts. Actually, we have been very impressed with the amount of power that the motor puts out even when running this high speed ratio. (NOTE: To maximize speed and reduce heat buildup Sherline recommends a slightly looser preload setting for turning high RPM. Instructions for adjusting preload are included with the kit.)
The pulley set is installed in about 10 minutes on your Sherline headstock. A new pair of split standoffs replaces the standard hex standoffs, as the new, larger pulley would not fit between the stock standoffs. All other guards and mounting points are retained, and the same belt is used. No special tools or modifications are required. In addition to the 10,000 RPM ratio, a second ratio that offers a maximum speed of about 2200 RPM is included. This is similar to the standard ratio on the normal pulley set for regular machining operations. (NOTE: Because of the split standoff design, changing pulley positions on the high speed pulley set is a little more time consuming than on the standard set, but is still easy to accomplish in just a few minutes.)
NOTE: This conversion is only designed for use with the DC motor in use since about 1993. Older AC/DC motors are identified by the smaller speed control housing and cannot be fitted with this pulley set.