The stone should run as true as possible.

It can be made true by using a piece of 1" gas pipe as a truing tool held against the stone when run dry.

Power grindstones usually have truing devices attached to them, Fig.221.A common form is a hardened steel screw, the thread of which, in working across the face of the grindstone, as they both revolve, shears off the face of the stone.

The surface should always be wet when in use both to carry off the particles of stone and steel, and thus preserve the cutting quality of the stone, and to keep the tool cool, as otherwise, its temper would be drawn, which would show by its turning blue.

But a grindstone should never stand in water or it would rot.
It is well to have the waste from the grindstone empty into a cisternlike box under it, Fig.221.In this box the sediment will settle while the water overflows from it into the drain.