BIT FOR ROTARY DRILLING Russian patent published in 1996 - IPC

FIELD: well drilling. SUBSTANCE: bit for rotary drilling has support members: bit paws 1 or blades 2 reinforced with hard alloy with mills installed on them, or cutters of diamond hard alloy plates 4. Support members are inclined at ψ angle to rotation axis. The angle is determined on the base on formula: , where v is angle formed by vector of relative speed of particles and drill rotation axis determined on the base of relation: , where he is sliding coefficient of fluid about drill bit; Wg is angle velocity of bit rotation, 1/s; D_k is diameter of the device in the area of support members, m; Vt is forward velocity of a particle taking into account its precipitation in flow m/s, support members has bevel in cross section. The bevel and well wall form wedge gap. Bevel angle (alpha) is directed backward from bit rotation and changes in the range of 0≅tgα<f, where f is friction coefficient of hard particles about rock, maximum value of the coefficient is determined on the base of formula: , where ρ-- is curvature radius of the support members in cross section, m. Radial gap is formed with minimum value equal to tripled value of critical size of particle in slurry intensive destruction of well walls begins from. EFFECT: high efficiency. 3 dwg