adding variable speed to one speed biax

If it is a brush type AC motor (Universal motor), then a router speed control will work just fine. A router speed control is pretty much a light dimmer with a little more circuitry. The technical term is Phase Angle Control. On the low end, about $15 from HF. The speed control is OK, but not great. I have used these on my router and other universal motors without problem. I did a quick search, and was not able to come up with a plug in 120V PWM controller.

If you want to spend the money, then a DC motor controller is a true PWM controller and will have much better control and torque characteristics than a router speed controller. Around $100 - $150

A good paper on the subject can be found here:

http://www.komel.katowice.pl/ZRODLA/FULL/84/ref_02.pdf
 
We can all :)). I was thinking try the device out on my 4" cheap angle grinder if it has the same style of motor. It is much cheaper than a biax if all does not go well. I have not yet heard from anyone at all yet that claims to have actually added variable speed to a power scraper. As such I will not risk it. Poor folks have poor ways. I could invest in this rather cheap control and risk the grinder, making the decision then as to whether or not to buy a single speed power scraper. I would also love to know more about the pwm set up. Even this rather expensive control on a used single speed biax would be much cheaper than I'm finding the variable speed ones. I looked at the paper, but must confess it gets too deep for me. I understand that the router control is the cheapest route with the poorest performance. I like the simplicity though. I could wire the pwm and other components with a lot of hand holding. I'm trying to avoid all that. Or if I knew how /where to shop and could pick up a proper single unit with Crayola simple directions I could cut a cord and wire it up. Love to hear what everyone has to say.
 
I worked in machine repair for 25 years and did a lot of power scraping with a biax, and for life of me don't know why you want to go variable speed. You have the stoke adjustment and that is the control you can use. I have also had a biax apart and they are a brush motor so a router control will work. I just plugged my Makita recipro saw into the router control and it worked fine.
 
Why do they make them variable speed now? Smarter folks than myself decided it was worth doing. I'm not ashamed to steal a page from their book.:)) Good to know there are folks out there that like the old ones too, though.
 
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