grinding wheels are fabricated with outwardly extending circular peripheral rims having a continuous rim surface to which separate abrasive pieces , preferably of a superabrasive such as cbn , are secured by suitable adhesive . the superabrasive pieces are preferably circular and of a diameter corresponding to the width of the rim and are secured to the rim surface so as to either be adjacent and touch one another or to be spaced one from the other around the circle of the rim surface so that a predetermined amount but not all of the rim surface is covered with abrasive pieces . that rim surface coverage optimize grinding efficiency while providing space for fluid flow for purposes of cooling and carrying away particles from the grinding process .