Measurements of Drilling Ability of Rotary Bits (Part 2)

Abstract By the use of a laboratory drilling equipment, behaviors of 33/4 in-two cone bits have been recorded. Bit weights continually vary from 50 to 150% of the mean weight, and these cause the variation in instantaneous drilling rate. There is a close relationship between the high weight and the high drilling rate: as an example, at a rotary speed of 22rpm the high instantaneous drilling rates ocucr. 0.3-0.5 seconds after the high bit weights. As a result of analyses of the relationship between the variations in bit weights and these in bit torques, it is found that smaller number of bit teeth penetrate into rock at a higher rotary speed.