Reducing Shaper RPMs

Advice on stepping down a shaper's drive motor to accommodate a sanding wheel. March 27, 2012

Question
Does anyone know how I can reduce the rpmís on a shaper/machine? I want to put a profile sanding head on a shaper, but need to reduce the RPMís. Iíve heard about inverters but donít know a lot about them.

Forum Responses
(Cabinetmaking Forum)
From contributor H:
Change the pulleys. Any bearing house will be able to compute the diameters to get the RPMís you need.



From the original questioner:
I canít change pulley on the spindle. There is not enough space for a bigger driven pulley. Could I change the pulley on the motor? The motor RPMís are 3600.


From contributor U:
If it is 3ph you could use the vf drive if you do not need to slow the motor down too much as this would heat the motor up. How much RPM reduction do you need?


From contributor G:
Looking around at spindle sanders it looks like you need to get to around 1750 RPMís. Most shapers lower speed is around 7000 RPMís. A large shaper might go down to 4K RPM. That's a long way to go. If it is a 3PH machine, like Contributor U suggested, a VFD will do the trick as long as you don't plan on making it a dedicated machine that will be used hours at a time.


From contributor Y:
Sit down before you look at the price of VFD's! Also, some motors will not be able to dissipate enough heat when running slower. They make motors that are specifically rated for VFD's.


From contributor W:
Swap motors. A 3600 rpm motor is unusual. Most are 1750. Another possibility would be to add a third pulley to the system. This very much depends on the clearances inside the cabinet.

In a nutshell: Replace the pulley on the motor with a step pulley. Run another step pulley on an independent shaft. That shaft has a second pulley that drives the spindle pulley. If the openings are in the wrong place, you may need to put the independent shaft where the motor is, and move the motor.