bit collar la and the adjacent blades 3 and extends downwardly where it curves inwardly to define a blade crown 5 and simultaneously outwardly in a blade sweep 6 that terminates near the center 16 of the bit body 2 as further illustrated in fig2 it will be appreciated from a further consideration of fig2 that the blade sweep 6 in each of the blades 3 is curved in the direction of bit rotation from the center 16 to facilitate mounting multiple cutting elements 9 therein in a selected offset and back rake and side rake angular configuration as hereinafter described as further illustrated in fig1 3 and 5 each of the cutting elements 9 is characterized by a flat cutting face 10 bounded by a circular cutting edge 11 with that portion or arc of the cutting edge 11 which extends farthest outwardly of the blade crown 5 of each of the blades 3 initially contacting and cutting a downhole interval not illustrated when the drill bit 1 is rotated by a drill string not illustrated in cutting configuration in a most preferred embodiment of the invention and referring again to fig5 of the drawing the cutting face 10 of each of the cutting elements 9 is altered and shaped by.