Using a speed control on a grinder?

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Forum topic by Bill White posted 07-20-2017 02:46 PM 318 views 0 times favorited 6 replies Add to Favorites Watch
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Bill White

4875 posts in 3891 days

07-20-2017 02:46 PM

Have a Dayton made Craftsman 7” bench grinder. 3450 rpm., 4.4 amp, 110 volts. Induction motor of course.
Would a fan speed control or light dimmer work to slow the speed without harming the motor?


6 replies so far

View Carloz's profile


1147 posts in 522 days

#1 posted 07-20-2017 03:12 PM

It will harm the motor big time but will not lower the speed.

View William Shelley's profile

William Shelley

543 posts in 1400 days

#2 posted 07-20-2017 03:16 PM

Find a 3-phase bench grinder and use a small VFD to control it’s speed.

-- Woodworking from an engineer's perspective

View Bill White's profile

Bill White

4875 posts in 3891 days

#3 posted 07-20-2017 03:33 PM

Why will it harm the motor? They work on induction motor ceiling fans. Just wantin’ to know.


View TheFridge's profile


9062 posts in 1417 days

#4 posted 07-20-2017 04:11 PM

Ceiling fans have more windings to accommodate speed. Typical induction motors are not capable of multi speed unless listed for that purpose (ex: some furnace fans)

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View JCamp's profile


538 posts in 481 days

#5 posted 07-20-2017 04:19 PM

Are you replacing a on/off switch with a variable speed switch or replacing a broken variable speed switch with a cheaper non name brand variable speed switch?
If it is the last one then no it wont hurt it. If its the first then yes it will work but id be afraid to try it on a good grinder just because it wasn’t made for it.

-- Whatsoever thy hand findeth to do, do it with all thy might

View MrRon's profile


4667 posts in 3174 days

#6 posted 07-20-2017 04:30 PM

You can’t control the speed of a single phase induction motor. Any speed control has to be built into the motor; no external device. A universal motor (brushes) can be controlled by a variable speed device.

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