It's always been my understanding that the controller you illustrate won't work. It may burn up your motor. That's what I have been told, anyway. I could be wrong. I'd like to be wrong on this one because the controllers that do work for sure start at $1,000.
The buffer, at $45, looks like a steal, but it's also only 1/2 horse. You'd be able to stop that one from spinning with any kind of force against the wheel at all. It might be ok if you go lightly and slowly. Anyone who has one should chime in.
My Baldor is a 3/4 horse and I can bog it down a bit at times, but it has enough power most of the time. One like mine will run you right at $500. Google around... maybe somebody can find a 115v/60h on the cheap and let us know. It's very helpful to have the long spindles. I also put a tapered spindle attachment on the left side of mine for quick-change capability of buffs
Yeah, I've read that those controllers will burn out buffer motors as well. I dont remember type of motor that a buffer has, but it isn't supposed to play nice with a speed controller like that.
I actually just got one of those harbor freight buffers, it seems to work fine. Having owned it about two weeks, I'm definitely not an expert, but I really havent had any problems with it slowing down b/c of pressure. As a matter of fact, I tried to bog the wheel down with greaseless to try to get it to stick better and had some trouble doing it. I may have gotten lucky though, I think harbor freight tools are hit or miss. The motor does seem to get really hot, though. Don't know if thats normal or not.
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If you keep an eye out you can prolly get that harbor freight buffer for even less. I got mine for about 36$. Harbor Freight has coupons everywhere. If you do a google search for a store near you you might get a "20% off any item in store" coupon through google offers. Thats what I got.