A resinoid-bonded grinding wheel employing hard abrasives such as cubic boron nitride or diamond is formed with a support member made of a vitrified grinding wheel. The support member has sealing layers on the surfaces thereof for avoiding the penetration of coolant into the support member. A method for forming the wheel includes mounting a grinding element on a radial peripheral surface portion of the support member and applying a sealing layer to the remaining surface portions of the grinding element for preventing penetration of the coolant into the support member and generation of vibrations in the grinding wheel during operation due to rotational imbalance caused by the presence of coolant within the support member.

A method for making grinding wheels having an annular grinding section mounted on a central hub in which a slurry of abrasive particles and ceramic bond is coated on a pre-formed core, shaped, and fired. Method has particular advantage in formation of wide wheels and contoured wheels. Premium abrasive may be employed in the wheels.

Enhanced micromachining rates are observed when lapping discs with standard SiO.sub.x lapping coatings are doped with trivalent or pentavalent additives, such as boron or phosphorous. Doping can be accomplished by subjecting the SiO.sub.x material to a "post glow", i.e., an argon plasma in the presence of a source of the dopant.

In accordance with the present invention, a composition of matter is provided for forming a vitrified abrasive wheel having an inner core and outer rim of differing compositions wherein said outer rim contains cubic boron nitride. The composition for the preferred rim material is a mixture comprising between about 10 to 70% by weight cubic boron nitride, between about 5 to 60% alumina, and about 15 to 35% bonding medium; and the preferred core composition comprises between about 10 to 65% silicon carbide, 10 to 60% alumina, and 5 to 30% bonding medium. In another aspect, a bonding medium is provided which is compatible with cubic boron nitride and in one embodiment has an oxide composition comprising about 71% silicon dioxide, 14% by weight boron oxide, about 5% by weight aluminum oxide, and about 10% by weight sodium oxide.

Bonded abrasive articles are described wherein a metal boride modified, lead-free vitreous matrix binds abrasive grains, such abrasive articles demonstrate improved performance over vitreous bonded abrasive articles with known vitreous matrices. Vitreous bond precursor materials are described including admixtures comprising lead-free vitreous precursor material and powder of metal boride(s), and admixtures comprising metal boride modified, lead-free vitreous particles. Methods are described for producing vitreous bonded abrasive articles having abrasive grains bound by metal boride modified, lead-free vitreous matrices.