This refers to machines that grind with the round outside. They run too fast for a water bath. Usually they have 2 grinding wheels on either side of the motor. Normally, the pulley diameter is relatively small at 150 mm, which is an advantage because it makes the hollow bevel deeper. To protect the steel from overheating, (relatively) slow-running types (e.g. 1450 rpm) are again recommended here. A CBN grinding wheel could also be advantageous here. I myself have little experience with this. Years ago I had a very fast running machine that was constantly giving me burnt out spots. That's why I have a slow running machine now.