Tech Talk
What are "Resin and Metal Bonded Wheels"?
Resin and Metal bonds are very closed structure systems and unless outside agents (such as glass spheres) are added, no controlled porosity (chip clearance) can be expected. Because of the lack of porosity and free exposure around the abrasive grains, a two step process is needed for truing and dressing. With resin you can true the wheel with either a rotary diamond of a silicon carbide brake-truing device. The same is true of Metal bond however for using the rotary diamond special concern must be placed on wheel to roll ratios.
The reason for dressing is to open the wheel and expose a percentage of the abrasive grain to allow for free cutting and chip clearance. The tool of choice is a soft bonded vitrified dressing stick made of friable aluminum oxide or silicon carbide and of a grit size smaller than CBN or diamond abrasive being dressed. To open the wheel, the stick is first soaked in coolant (to reduce abrasive dust) and then forced into the wheel face. The resistance will be reduced as the bond is eroded and the abrasive is exposed. The best process is to use a given cubic inch of stick per area of wheel per dress. Although there are studies regarding ration the going practice is to measure the amount of stick used when you feel no more resistance between the wheel and the stick. This process can be done either by hand or with a mechanical feed into a stationary mounted stick.
