Abstract: In the drilling operation of deviating and adjusting azimuth for directional and horizontal wells, the function of gage sidecutting of the bit is one of the important factors affecting the rate of penetration and the quality of well profile. In this study,the gage cutters' movement of a tricone bit was simulated, in which the gage cutters' scraping the rock around the wellbore
and the formation of transition zone were visualized. A testing device was set up and experiments of rock failure by inserts were carried out on selected typical rock samples and by combining various tooth shapes, various cutting structures and different testing parameters. The suffered load on tooth was also analyzed. The result of this study provides technical basis for deter-
mining gage cutters’shape and designing cutting structure, and has been used with success in the design of the first tricone bitspecial for deviating and adjusting azimuth in China.

Key words: tricone bit, deviating, side-cutting, simulation, force analysis, bit design