row of free running, hardened and serrated, wavy discs or star-shaped cutters running at right angles to the handle. These are presented to the grinding wheel as power is turned off and the wheel slows down. Force is applied to the face of the slowing wheel with the result that the hardened discs match speed with the face of the wheel allowing the fingers or undulating surface of the dresser, to knock the abrasive grains out. Diamond dressers — Shorter handled diamond tools that either have a matrix of small diamonds bonded to a broad surface on the end of the dresser (top image) or a single diamond mounted in their face (lower image). As the diamond is introduced to the wheel's face, the harder diamond remains attached and the looser grains fall away. Dressing sticks — A stick of hard material, usually made from the same materials (silicon carbide) but with a stronger bonding agent. NorBide is one brand of dressing stick made by Norton Abrasives from boron nitride. Also an abrasive wheel type that has a small "grinding wheel" in a holder that is held against the spinning grinding wheel to dress and clean the face of the grinding wheel. Grinding complex shapes Four types of dressers are used to dress the wheels of CNC grinders used for grinding complex shapes. This type of dresser is mainly in use on CNC grinding machine tools to automatically dress the grinding wheel via computer control in specialist areas requiring complex shapes such as grinding bearing raceways. Stationary dressers — a stationary dresser can have multiple diamonds hand set or a (mesh) across a given width. These type tools are typically used to dress straight faced wheels. Stationary tools can also be a single diamond brazed into the tip and ground to a specific radius size. A CNC dressing program will utilize this specific tool nose radius offset and move it across the face of the wheel, moving in and out to create the desired profile. The grinding wheel's profile is controlled by the CNC program used to dress the wheel, rather than by the profile of the dresser itself. Crush rolls — a crush roll is a high-speed steel or tungsten carbide wheel. Its profile is the mirror image of the desired profile of the grinding wheel. It is forced against the grinding wheel, while spinning at the same surface