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Using a speed control on a grinder?

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Forum topic by Bill White posted 07-20-2017 02:46 PM 406 views 0 times favorited 6 replies Add to Favorites Watch
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Bill White

5124 posts in 4160 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?
Bill

-- bill@magraphics.us


6 replies so far

View Carloz's profile

Carloz

1147 posts in 791 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

595 posts in 1669 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

5124 posts in 4160 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.
Bill

-- bill@magraphics.us

View TheFridge's profile

TheFridge

10718 posts in 1686 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

JCamp

877 posts in 750 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

MrRon

5192 posts in 3443 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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