Analytical and experimental study of determining the optimal number of wedge shape cutting teeth in coring bits used in percussive drilling

In this paper we study the design of the coring bits with wedge-shape cutting teeth of vibratory drills that percussively penetrate into brittle material. The overall coring bit specific energy is analytically derived as a function of the cutting teeth spacing and teeth number. It is found that given the coring bit dimensions and rock material properties, there exist an optimal spacing/depth ratio and an optimal tooth number that minimize the coring bit specific energy and hence maximize the coring bit's drilling rate. Experimental drilling tests were performed to corroborate the analytical results. It was shown that the laboratory drilling tests follow the trend predicted by the theoretical analysis. [DOI: 10.1115/1.2515345]