a fixed guide wheel that when coupled to a saw blade or a grinding wheel provides a sawing or grinding system that will control the exact depth at which the tools are allowed to perform . the guide wheel also rolls along the top surface of the work piece pushing down on it while the cutting or grinding process is occurring . the guide wheel has a central bearing that carries the saw blade or grinding wheel across the surface of the stone keeping the tools centered and balanced with each other . the guide wheel is made from a rigid , low - density material that absorbs vibration that would normally transfer from the grinding wheel to the material being cut .