When buying a new motor, many of them come with both 56C mounting face and a base bolted on, so you get both for same price. The Iron Horse motors are the least expensive ($127 shipped for 2hp, 3ph) of any new motor I've found, and they seem to work just fine. If you find a used motor, then you might have more options. Had I considered it, I might have mounted my motor using base plate rather than 56C plate. It was a good bit of work machining that mounting plate. The more I think of it, the more I think the base plate mount would be just as good, and allow an extra adjustment for alignment.
For the grinder built you posted the photo of, I "think" I'd prefer the base plate mount to 56C mount. With base mount, you could use one of those motors you mentioned laying around to mount and test grinder while deciding on motor/VFD combo. You would have only 1 speed. If you've got the shaft, pulleys, etc you "could" do the extra work involved to start with a 3 step pulley setup, then change to 3ph & VFD later at no additional cost, since you would not have spent any money on the test 1ph motor and pulley setup. "IF" you have to buy motor, pulleys, belt, shaft, bearings, etc - that will cost about the same as buying the 3ph motor and VFD - using the links I provided before.
That was why I built with a pulley setup for first grinder - I had motor, belt, pulley, shaft on hand so had no real cost involved. After using that for a yr I got the itch for a variable speed. I thought about adding variable speed to the grinder I had, but wound up selling it for more than it cost me to build the one I have now with variable speed. As I've stated before, while using the pulley I didn't really think there was any real need for a variable speed, but finally decided to try it. After using the variable speed - WOW!! I've posted a couple of times "I have to eat crow" on the need for variable speed. I had no idea how often I'd be at 500 SFPM when doing a final grind on fitting parts. Also, when using 600, 800, or even 2,000 grit belt, a slow speed is VERY important so as not to "burn" with that fine grit.
Ken H>
For the grinder built you posted the photo of, I "think" I'd prefer the base plate mount to 56C mount. With base mount, you could use one of those motors you mentioned laying around to mount and test grinder while deciding on motor/VFD combo. You would have only 1 speed. If you've got the shaft, pulleys, etc you "could" do the extra work involved to start with a 3 step pulley setup, then change to 3ph & VFD later at no additional cost, since you would not have spent any money on the test 1ph motor and pulley setup. "IF" you have to buy motor, pulleys, belt, shaft, bearings, etc - that will cost about the same as buying the 3ph motor and VFD - using the links I provided before.
That was why I built with a pulley setup for first grinder - I had motor, belt, pulley, shaft on hand so had no real cost involved. After using that for a yr I got the itch for a variable speed. I thought about adding variable speed to the grinder I had, but wound up selling it for more than it cost me to build the one I have now with variable speed. As I've stated before, while using the pulley I didn't really think there was any real need for a variable speed, but finally decided to try it. After using the variable speed - WOW!! I've posted a couple of times "I have to eat crow" on the need for variable speed. I had no idea how often I'd be at 500 SFPM when doing a final grind on fitting parts. Also, when using 600, 800, or even 2,000 grit belt, a slow speed is VERY important so as not to "burn" with that fine grit.
Ken H>
Got a team of 4 guys together to bowl a tournament. We're currently in 1st for $3000! $750 isn't a bad cut for an average day of bowling. Guess what i'll be spending most of that on? 
