Polycrystalline diamond (referred to as PCD) is formed in a large High Temperature-High Pressure (HT-HP) press, as either a diamond wafer on a backing of carbide, or forming a 'vein' of diamond within a carbide wafer or rod.
Most wafers are polished to a mirror finish then cut with an Electric Discharge Machine (EDM) into smaller workable segments that are then brazed onto the sawblade, reamer, drill or other tool. Often they are EDM machined and/or ground an additional time to expose the vein of diamond along the cutting edge. Today these tools are mostly used for machining of nonmetallic and nonferrous materials.
The grinding operation is combined with EDM for several reasons. For example, according to Modern Machine Shop, the combination allows a higher material removal rate and is therefore more cost effective. Also, the EDM process slightly affects the surface finish. Grinding is used on the affected zone to remove the effected area and provide a finer final surface. Along the same lines, Beijing Institute of Electro-Machining attributes a finer shaping and surface geometry to the compilation of the two processes into one.
The process itself is accomplished by combining the two elements each individual process into one wheel. The diamond graphite wheel accomplishes the task of grinding while the graphite ring around the existing wheel serves as the EDM portion. However, since diamond is not a conductive material, the bonding in the PCD work piece must be ample enough to generate the conductivity necessary for the EDG process to work.