a rotary drill bit comprises a bit body having a shank for connection to a drill string , a plurality of cutters mounted on the bit body , each cutter having a cutting face , and means for supplying drilling fluid to the surface of the bit body to cool and clean the cutters . at least some of the cutters are lateral cutters located to act sideways on the formation being drilled , and the cutting faces of such lateral cutters are orientated to exhibit negative side rake and negative top rake with respect to the surface of the formation . the negative side rake angle is greater than 20 ° and may be as much as 90 °, and the negative top rake angle is also more than 20 °. a single cutter may include two cutting faces at different negative side rake angles , e . g . the cutter may comprise a generally cylindrical substrate formed at one end with two oppositely inclined surfaces meeting along a ridge , a facing table of polycrystalline diamond being bonded to the substrate surfaces and extending over the ridge .