The speed of your machine will depend on the size of your disk. Remember that diamonds like to run fast and, although you can run them slower, their efficiency will be greatly compromised by slower speeds.
Our recommendations for shaft speed are these:
|12 – 14 inch disk||1050 – 1575 RPM|
|16 inch disk||800 – 1200 RPM|
|18 – 20 inch disk||700 – 1050 RPM|
|24 inch disk||500 – 750 RPM|
If you are only grinding with your machine, stick to the high end of the scale, if you'll be grinding and polishing with your machine, go for the lower end. You won't see a lot of difference in the grinding efficiency, but you'll really need that lower speed when you go to use your polishing pad
The best of both worlds would be a variable speed machine that will accommodate both faster grinding and slower polishing.