Evaluation of the permissible moment in a roller cone drill bit providing the prescribed reliability of work

Abstract

After analyzing the nature of the damage of surfaces was discovered the traces of the compression effect which arise along the cutters axis when squeezing it into the rock of delve. There were also founded the traces of deformation from the action of bending to the cutter, depending on the orientation of its slip on the face. We noticed the rubbing, fretting-corrosion, damage the local areas of the apertures walls caused by scrolling the cutter around its axis in the aperture of cones crown. In the case of the use of cutters with symmetrical aggravation of the rockdestructive part, the orientation of the generating line of active part of the cutter is determined by an effective angle to the axis of the crown of the cone. Calculations show that an angle of 45° is optimal. We noticed the rubbing, fretting-corrosion, damage the local areas of the apertures walls caused by scrolling the cutter around its axis in the aperture of cones crown. The analysis of types of rock-destructive equipment of cones damages has been revealed that with increasing the magnitude of the axial load on the bit, cases of splitting, destruction of hard-alloyed cutters increase. For this purpose, it is necessary to protect the drill`s crowns from cementation. If carbide cutters are located in several rows in the cone drill, then milling of the sites on cemented layer`s depth is effective. This prevents the removal of parts of cone`s crown. The allowable moment is proportional to the square of the height, so the connections which perceive the considerable bending moments cannot be performed with small values of the diameter or small height of the cutter shank.