a cutting structure for a rotary drill bit includes a cutting element 30 having a front layer 32 formed of polycrystalline diamond , bonded to a backing layer 33 formed of tungsten carbide . the cutting element is bonded to a carrier 33 which is formed of a number of detachable individual elements having means holding them in position such that , upon wear of the cutting structure in use , the holding means of an element engaging the formation will eventually fail , causing detachment of that element from the carrier , and thereby reducing the area of the cutting structure in contact with the formation .