Upon completion of the mechanical truing process (run-out), a brake truing device, single point diamond dresser, diamond nib, metal bonded wheel or, rotary diamond dresser will be used to complete the truing process for all bonds except plated. Using one of the aforementioned devices the wheel should be trued until a reading on the indicator of ≤ 0.0002” (0.005mm) has been achieved. The abrasive and the bond type are the most important criteria for deciding the type of truing and/or dressing system to use. For truing only with a point contact such as a single point or specific radius rotary dresser I would never recommend in-feeds of more than 0.0004” (0.010mm) per pass for Superabrasives (CBN or Diamond) or, more than 0.00075” (0.019mm) per pass for conventional abrasives.
Grinding Wheel Truing and Dressing
Conventional abrasives (aluminum oxide and silicon carbide) can be trued and dressed at the same time, using a single point dresser. The conventional abrasive is quite friable (friability = ease by which an abrasive fractures). This means a quality diamond with a carat size appropriate for the diameter of the wheel its thickness and abrasive grain size. Note: Among other options, an alternative to a single point is the “rod diamond”, utilizing a man made diamond in the shape of a rod. This is not a PCD (polycrystalline diamond) but a grown diamond.
Dressing involves the same aforementioned tools as discussed for truing, with the exception of the “brake truing device” and, for dressing resin and metal bonds used with Superabrasives would include but not limited to “the abrasive stick” (typical size ¾” x ¾” x4”). The purpose is to open the wheel face and prepare the grinding wheel surface for achieving both dimensional tolerances demanded by the part geometry and establish a specific finish requirement on the part surface. For dressing I would never recommend in-feeds of more than 0.0001” (0.0025mm) per pass for Superabrasives (CBN or Diamond) or, more than 0.0005” (0.0127mm) per pass for conventional abrasives.
The process for truing and dressing vitrified CBN is very similar to that of conventional abrasives with the exception of in-feed per pass. The plated process (used in Superabrasives) is not a viable option for truing and vitrified diamond is only different in that single point dressing is not applicable and the wheel to roll ratio for the rotary dressing systems is different (> 5:1 roll to wheel). Truing and dressing will also be covered in the following section for bond types.
