Analysis designed diameter of cone bit

Based on tricone bit geometry and kinematics principles, the article expounded the related factors that affect the bit diameter, and the relationship between the relevant structural parameters and the bit diameter. And taking the specific bit as the example, we quantitative analysis the influence situation of the tolerance of relevant parts to the bit diameter with the application software, and the relationship between parts of the machining error with the error of the bit diameter. At the same time, we quantitative descript the distribution of the bit diameter error with the random variable´s probability distribution theory, and calculate the qualified rate of the bit design diameter according to the design data. And we proposed the diameter control method of the design stage, which provides a theoretical basis and measures about the reasonable determination related parameter tolerance when designing the bit.