Abrasive bodies

A drill crown including a rotatable circular end having mounted therein a plurality of abrasive bodies, each abrasive body including an abrasive compact comprising a mass of diamond or cubic boron nitride particles, present in an amount of at least 70 percent by volume of the compact, bonded into a hard conglomerate and support means covering a part of the surface of the compact and bonded to the compact, wherein the support means covers more than 50 percent of the surface of the compact and wherein the compact is in the form of a circular disc embedded in the support means so as to provide an exposed arcuate surface or edge which extends over less than 50 percent of the circumference of the disc and which provides an abrading formation,

• the support means of each abrasive body being embedded in the circular end of the crown and secured thereto by brazing and the exposed arcuate surface or edge of each body presenting an exposed abrading formation for the crown.