Ural State Mining University, Yekaterinburg, Russia:

D. I. Simisinov, Deputy Vice-Principal of Science, Candidate of Engineering Sciences, 7sinov@mail.ru
A. I. Afanasiev, Professor, Doctor of Engineering Sciences
V. S. Shestakov, Professor, Candidate of Engineering Sciences
N. G. Valiev, Head of Chair, Professor, Candidate of Engineering

Design development of roller bits is a complicated engineering problem. It is rather difficult to create an adequate strong bearing with sufficiently effective set of roller cutters. Endurance and operational integrity of roller bits is the key factor of their life duration. The developed back-to-back endurance design procedure for roller bit bearing includes calculations of loads on roller bearings of the bit leg, their distribution on the bearings, number of rolling bodies taking the loads and contact stresses. The back-to-back endurance design of bearing races is carried out in accord with linear theory of summing damages over the drill bit life. In the program written for the back-to-back endurance and time to failure of a bit bearing, the calculations are performed by the roller–ball–roller scheme for a drill bit with a diameter of 250.8 mm. The design procedure to the utmost includes structural features of roller drill bits and drilling practice parameters capable to affect operation integrity of the tool with regard to random distribution of values of the parameters. All in all, 33 structural, technological and operating indices of drill bits are included.
The study was supported by the Ministry of Education and Science of Russia under the state contract with the Ural State Mining University for 2019.

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