Abstract: A rotary drill bit for use in drilling or coring deep holes in subsurface formations comprises a bit body having a shank for connection to a drill string and a plurality of cutting elements mounted at the surface of the bit body. Each cutting element is bonded to a stud which is received in a socket in the bit body. Spaced rearwardly of each cutting element is a separate abrasion element comprising a stud which is received in a socket in the bit body and is impregnated with particles of natural or synthetic diamond. The abrasion element provides a back-up in the event of failure or excessive wear of the cutting element and its spacing from the cutting element prevents the damaging transfer of heat from the abrasion element to the cutting element. The cooling may be enhanced by providing a channel for drilling fluid between the cutting element and abrasion element.