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A wheel dresser is a tool used for refurbishing or dressing the abrasive wheels of a bench grinder. These grinding wheels wear away and become clogged with use and typically develop either chamfered or beveled edges or a hollowed out central area. This can weaken and unbalance the grinding wheel and cause it to fracture during use and seriously injure the user. Clogging of the abrasive surface of the wheel also diminishes its efficacy to the point where the grinder no longer functions. To restore the profile and efficiency of the grinding wheel to its original state, a wheel dresser is laid on the tool rest and pressed against the grinding wheel while it is turning to refurbish it.
Grinding wheels are made of a granular abrasive compound mixed with a bonding agent and pressed into shape. With use, this abrasive matrix is dislodged from the wheel causing the original profile to degrade and the remaining abrasive particles to become dull and rounded. At the same time, the wheel picks up particles of the work piece material which clog the pores or spaces between the abrasive grains. This leads to the smoothing or glazing of the wheels surface which is often seen as shiny, reflective areas. To rectify these conditions, the wheel needs to be dressed or refurbished using a wheel dresser.
A wheel dresser is typically a long handle with a variety of different tool heads attached. One of the most common is the star dresser which consists of a number of free spinning, hardened discs arranged at right angles to the handle. These discs are serrated or toothed and held in a U-shaped frame with a tool rest lip on the underside. To dress the wheel, the grinder is turned on and allowed to reach its maximum operational speed then turned off again. The tool rest lip is then hooked over the tool rest to ensure steady operation and the serrated disks brought to bear against the slowing wheel.
As force is applied to the wheel dresser, the discs rotate at the same speed as the wheel and the serrations or fingers of the discs dislodge a layer of dull abrasive and any foreign material lodged on its surface. This exposes fresh abrasive and evens out any worn out areas of the wheel. Other types of wheel dressers include dressing sticks, which are made of the same material as the wheel with a far stronger bonding agent, and diamond dressers which have a single industrial diamond or a matrix of finer diamonds on their tips. These all fulfill the same function of exposing fresh abrasive and removing foreign material by dislodging worn abrasive from the grinding wheel.