Converting to Electronic Variable Speed

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Forum topic by Linz posted 05-17-2008 01:18 AM 3661 views 0 times favorited 5 replies Add to Favorites Watch
View Linz's profile


3 posts in 3903 days

05-17-2008 01:18 AM

Topic tags/keywords: variable speed shopsmith conversion

Having an older Shopsmith 10ER with a tired motor, I would like to convert to an electronically variable speed set-up. I am not opposed to spending the money on a new motor and control but am having trouble finding anyone who can tell me exactly what to purchase. Anyone done such before? What type motor is best? What type control?

-- Linz - Ann Arbor

5 replies so far

View Randolph Torres's profile

Randolph Torres

295 posts in 3769 days

#1 posted 09-28-2008 08:12 AM

Linz: You can pick up single phase variable frequency drive units from electrical supply stores make sure you take you motor name tag info so they can supply you with a motor that is equlivent, mounts the same and is also compatible with frequency drives. Randolph@cooperedpatterns

-- another tip from cooperedpatterns

View marcb's profile


768 posts in 3914 days

#2 posted 09-28-2008 08:43 AM

There’s a few options. A 3 Phase motor and a VFD will do what you want.

So will a DC powered Motor and a Motor Controller circuit that has speed control (preferably PWM, but others work fine too).

There are some other options as well, but those are the 2 that I understand the best.

View Planeman's profile


97 posts in 3818 days

#3 posted 09-28-2008 06:49 PM

The guys in the Home Shop Machinist web discussion site are having a lot of success using the motors and electricals from used exercise tread mills. These are often obtained for FREE from your local Craig’s List “free” web site from people who just want these things out of their house. They are often running metal lathes using these motors which are variable speed with a wide speed range.


-- Always remember half of the people in this country are below average.

View fredf's profile


495 posts in 3951 days

#4 posted 09-29-2008 09:53 PM

Planeman—Thanks for the Home Shop Machinist site what a great site, and what a great idea to re purpose treadmill motors!

-- Fred, Springfield, Ma

View 8iowa's profile


1591 posts in 4002 days

#5 posted 10-11-2008 05:37 PM


With an AC variable speed controller (varies frequency) or a DC motor, keep in mind the fact that this type of variable speed power supply operates at constant torque from it’s base speed. In other words, if you 1/2 the motor speed, you also 1/2 the HP.

Thus, if you are thinking that this would be a good way to drill with that 3” forstner bit you will be disappointed.

-- "Heaven is North of the Bridge"

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