Grinding dresser

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

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. 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. 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.

They are available as:
* 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 survives the contest 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.