Rotary drill bit with cutting insert having edge preparation

摘要

A rotary drill bit for engaging an earth strata material includes an elongate drill bit body having an axial forward end and an axial rearward end, and a cutting insert attached to the axial forward end of the elongate drill bit body. The cutting insert has an elongate insert body rotatable about a central axis and includes a pair of symmetrical halves symmetrical about the central axis, each symmetrical half including a leading face, a top surface having a relief surface, a T-land surface extending between the leading face and the relief surface and a cutting edge formed at the intersection of the T-land surface and the relief surface. The cutting edge can have a negative axial rake angle. The relief surface can include a primary relief surface and a secondary relief surface.

主权项

1. A rotary drill bit for engaging an earth strata material, the rotary drill bit comprising:
an elongate drill bit body having an axial forward end and an axial rearward end; and a cutting insert attached to the axial forward end of the elongate drill bit body, the cutting insert having an elongate insert body rotatable about a central axis, the elongate insert body having a pair of symmetrical halves symmetrical about the central axis, each symmetrical half comprising: a leading face; a top surface having a primary relief surface and a secondary relief surface, wherein the primary relief surface is perpendicular to the leading face; a T-land surface extending between the leading face and the primary relief surface of the top surface; and a cutting edge formed at the intersection of the T-land surface and the primary relief surface of the top surface; wherein the secondary relief surface extends continuously from the primary relief surface to a rearward face of the cutting insert.