# Variable speed 'box' for fixed speed die grinder?



## petertha (May 26, 2018)

I purchased this Bosch die grinder because the price & size was right. Or so I assumed. On Amazon they list it as variable speed, which is actually 100% INCORRECT. It is most certainly 1-speed. I used it, time passed, thought I'd live with it. But now (that its too late) having buyers remorse. For any tooling that is much larger than typical small diameter burrs, especially like 2" flap or abrasive mesh pads/wheels, its actually borderline scary dangerous. The 'real' variable speed models are bigger, heavier & more $$.

Is there any kind of aftermarket 'box' I can acquire to control the speed externally? ie plug the grinder into the box & turn a dial to give me progressive rpm? I know this used to be a thing back in the day with Variacs (does that mean variable voltage transformers?). But how would I know this motor is compatible? I assume true variable speed motors in tooling must have brushless motors & dedicated controller circuit board thingy inside? In case you were wondering based on my sophisticated electrical vocabulary I am not a PhD electrical engineer - LOL


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## machinejack (May 26, 2018)

If it's a brushed universal motor varying the voltage will control it, but you loose power at lower rpm.  PWM would be the way to do it.


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## Buffalo21 (May 26, 2018)

Harbor Freight #43068 ??

I saw my mistake #43060


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## hman (May 26, 2018)

43060
https://www.harborfreight.com/router-speed-control-43060.html
$20


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## wcunning (May 26, 2018)

You want a Variac. I suggest getting one of the better American made ones used off of eBay over something else. It's kinder to your motor than the HF junk *ahem* speed controller. I use one on my Biax power scraper and love the heck out of it, plus I could use it on angle grinders or die grinders if I so chose. 

Cheers,
Will


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## f350ca (May 26, 2018)

They list it as having soft start, as far as I know you can't use a variac or router speed control on it.  Hopefully someone with experience will confirm or deny this.
I have an old Makita die grinder that I have used a variac on when carving wood with it. Works fine. Want to try a router speed controller at some point.

Greg


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## petertha (May 26, 2018)

F350ca, where did you see that soft start spec? I missed that detail. Dangit.

This speed control looked interesting, but note the critical comment.
https://www.amazon.ca/MLCS-9410-20-...s/B001NIK6PC/ref=dpx_acr_txt?showViewpoints=1

the same as all the lookalikes or...?
https://www.amazon.ca/Yeeco-Control...06WRMWK3W/ref=cm_cr_arp_d_product_top?ie=UTF8


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## f350ca (May 27, 2018)

Bosch's web site lists it as having constant response with soft start.

https://www.boschtools.com/ca/en/boschtools-ocs/die-grinders-dg250c-36138-p


Greg


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## Downunder Bob (May 27, 2018)

Any hobby electronic store should have a speed control kit, ok you have to put it together yourself but they are pretty easy, just follow the instructions, Just make sure the kit can handle the wattage of the die grinder, should be ok.


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