GREAT information, and nice job on the controller.
I lucked out at a garage sale. Crowds of people had already been through and ignored several of the tubs filled with aluminum scraps and odds and ends. One had what looked like a motor I'd been eyeballing on line for several years - an industrial sewing machine motor. I bought that bin for twenty, along with a few more equally impressive finds.
The motor had a 3/4 horse DC motor and controller. I'd bought a four wheel grinder of craigslist for a couple hundred and it was running on 240. I pulled the motor and swapped it for the garage sale find. I, now, have one of the nicest grinders you could buy. I can run the wheels at from 5 RPM's to 2,400 RPM, so overheating things is less likely and controlling the grind is far easier now. Especially since I swapped out two of the wheels for CBN's.
I like the performance of the grinder so much, I ran an add for free treadmills. Two responses gave me a 1hp and a 3/4 horse DC motor. Because rectifiers and things are so cheap, I built a controller to swap out my the dental lathe (strange name for a buffer) on my Handler buffer from 1/3hp, two speed Redwing to a variable speed treadmill motor.
Both motors tested good on my DC controller and it looks like my buff station and drill press will be going variable speed in the future (have to pick up a couple tacs for RPM monitoring).
Sure beats spending the extra $1,000.00 for the variable speed capability.