A grinding dresser or wheel dresser is a tool to dress the surface of a grinding wheel

Grinding wheel

A grinding wheel is an expendable wheel that is composed of an abrasive compound used for various grinding and abrasive machining operations...

. Grinding dressers are used for making different profile on grinding wheel. The dressing of a wheel in order to return the wheel to its original shape. Truing is also a method of wheel balancing.

Purpose

The objective of dressing the wheel is to:

• True the wheel by knocking abrasive particles from the wheel's surface and making the wheel concentric
  Concentric
  Concentric objects share the same center, axis or origin with one inside the other. Circles, tubes, cylindrical shafts, disks, and spheres may be concentric to one another...
  
  . This minimizes vibration and improves surface finish, eliminating the vibration of the out-of-balance wheel across the workpiece's surface.
• Dislodge these same abrasive particles, which also has the effect of exposing fresh abrasive from the wheel's surface. Each abrasive grain is a small cutting tool; a worn grain has its edges dulled and loses its effectiveness. Exposing the fresh grains is thus a sharpening process. Glazing of the wheel is evidence of rounded grains and is noticeable by a reflective surface on the spinning wheel.
• Clean the wheel. If a workpiece is softer than the grade for which the wheel is designed, the abrasive particles will not be dislodged in time to present fresh, sharp grains. The wheel therefore appears to lose its edge especially as the pores between grains fill with fragments of the workpiece. The wheel is then said to be loaded and is one reason why the selection of wheel is extremely important.

Types

• Star dressers — A long handled tool with a row of free running, hardened and serrated, discs running at right angles to the handle. These are presented to the grinding wheel as it is turned off and 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 carbide.

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 is a metal blade with a single diamond brazed into the tip. A CNC dressing program moves 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 speed as the grinding wheel. Doing so breaks the bond between the abrasive particles on the surface of the wheel, exposing a new surface as particles fall away. One disadvantage is that the wheel profile cannot be adjusted except by replacing the roll with one having a different profile.
• Diamond crush rolls — a diamond crush roll is a crush roll coated with diamond particles. It wears more slowly. Less wear means they can be used to achieve tighter tolerances than crush rolls.
• Rotary dressers — a rotary dresser (sometimes referred to as a pizza-cutter dresser) is a disc with a hard material - usually diamond - attached to the edge. 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.