[How do I?] Variable speed grinder

[DavidR8]

Is it possible to add a variable speed control to a run-of-the-mill bench grinder?
I see that Delta makes a 6" and 8" variable speed model that looks identical to a non-variable speed version.
I thought just buying the speed control part might be the ticket but I see that it has a PC control board so there's obviously more to it than a rheostat.

 

[Tozguy]

Are you referring to something like this?

ROUTER SPEED CONTROL 115V 15A

With this variable speed control you can reduce the speed for larger bit routing specially when doing raised panelling.

www.busybeetools.com

 

[darkzero]

I'm no motor expert (paging the Doc @Ulma Doctor) but I do know those router speed controllers can only be used with brushed motors which bench grinders usually do not have. I've had one of those for like 25 yrs & I can't ever remember using it.

 

[Ulma Doctor]

I'm no motor expert (paging the Doc @Ulma Doctor) but I do know those router speed controllers can only be used with brushed motors which bench grinders usually do not have. I've had one of those for like 25 yrs & I can't ever remember using it.

just a clarification....
i have successfully used a router speed controller to control brushless motors on fans
the motor doesn't necessarily have to be brushed to function.
the intention is for small motors of less than 1 hp with the router speed controller (15amps AC/DC universal type motor is advertised)

you can't start in the low speed setting, the motor is started in high speed, then reduced.
the technology is PWM, pulse width modulation in both the VFD as well as the humble router speed controller.
mind you, that there can't be a capacitor in the circuit, as the PWM doesn't play well with capacitor start or capacitor run systems

 

[CluelessNewB]

I believe the Jet variable speed grinder is a 3 phase motor with a VFD. The Delta says it is an induction motor, it might also be 3 phase with a VFD but... it also lists a separate capacitor in the parts list, has a relatively low price and a limited speed range... I suspect some trickery less than a "real" VFD.

 

[DavidR8]

just a clarification....
i have successfully used a router speed controller to control brushless motors on fans
the motor doesn't necessarily have to be brushed to function.
the intention is for small motors of less than 1 hp with the router speed controller (15amps AC/DC universal type motor is advertised)

you can't start in the low speed setting, the motor is started in high speed, then reduced.
the technology is PWM, pulse width modulation in both the VFD as well as the humble router speed controller.
mind you, that there can't be a capacitor in the circuit, as the PWM doesn't play well with capacitor start or capacitor run systems

Thanks,
I wonder if it’s worth my while to try a router speed control on my grinder.
I can get one for a few dollars and might do the trick.


Sent from my iPhone using Tapatalk

 

[ddillman]

Can't hurt to try. If it burns up the grinder motor then you can buy a variable speed grinder. I use my speed control on the vacuum cleaner when I have it hooked to the sand blaster cabinet to slow the vacuum cleaner down a little bit.

 

[Tozguy]

I have used the controller shown above with a Dewalt cut out tool (30,000 rpm) and on a Delta contractor circular saw, both with no problems.
However these where shots in the dark and I am glad to have info about avoiding capacitor motors...thanks Doc.

 

[Alcap]

Glad to learn of more uses for the router speed control I have , only used it once 20+ years ago on a router bit that was pretty big for the single speed router I had at the time . I hope others post of other uses .

 

[C-Bag]

My router speed control lives with my Foredom grinder because the little angle head grinder shouldn’t be run at full rpm. Works good and has eliminated the foot pedal that came with the Foredom. I’ve also used the SC on my HF die grinder to slow it down and it worked flawlessly.

Are you wanting to slow your grinder down David for like honing lathe bits? Many times faster is not better for me as it’s easier to control finishes at a slower rpm.