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What is The Difference Between Dressing and Truing? | CRATEX Abrasives

This article is part of Silicon Carbide Grinding Wheel Dresser series.
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Both dressing and truing must be conducted in the purpose of creating satisfactory work. Both operations remove material from the grinding wheel. While dressing relates to a surface finish maintenance, truing relates to the loss of form control due to the excessive edge wear.

Although sometimes together referred to as ‘conditioning’, they mean two different operations. Conventional grinding wheels that are inexpensive can be trued and dressed at the same time and the process can be repeated periodically. However, superabrasive grinding wheels, like CBN or diamond wheels, are a serious investment and require much more attention to dressing and truing separately.

Truing is done when a new wheel is installed and before it’s used for the first time and is necessary for precision grinding. The purpose of truing is to bring every point of the grinding surface concentric with the machine spindle (to establish concentricity) and to introduce a form (shape) into a wheel. No matter how precisely manufactured, there will be a slight gap between the wheel bore and the machine spindle. Even if the gap is one thousand of a millimeter, problems like chatter marks will occur if the wheel is not trued to the center of the spindle. Conventional grinding wheels can be trued easily with a diamond cutter that is harder than the wheel, while the superabrasives cannot be cut and must be ground to size. This is done by using a sintered diamond roller or by traversing a conventional grinding wheel. Many like to use a brake-controlled truing device called BCTD which turns more slowly and provides a more precise and controllable truing. After the truing process, the wheel surface is smooth and closed, and since there are no abrasive grits exposed, the wheel can’t perform cutting.

Dressing is the process that comes after truing (especially in the case of superabrasives) and it represents grinding wheel sharpening by exposing abrasive grits above the bond. In other words, removing small chips of workpiece lodged in the wheel surface or removing dull abrasives which returns the wheel to its original dimensions and provides crystal exposure. The wheel surface after dressing is open with grits exposed.