Patent ID: 6129162
Filing Date: 2000-10-10
Classification: E21B

Abstract:
A rock drill comprises an axially extending drill shaft (2) having a first end and a second end with at least one helical drilled material removal groove extending from adjacent the first end toward the second end, a drillhead (5; 50) formed of a hard metal alloy securely attached to and projecting axially outwardly from the first end of said drill shaft (2), said drillhead transversely of the axial direction of said drill shaft has a long direction and a short direction extending transversely of the long direction with a first diagonal (D1) extending generally in the long direction and a second diagonal (D2) intersecting said first diagonal at approximately the axis of said drill shaft and extending generally in the long direction, a main cutter (6; 60) formed by said drillhead extending along said first diagonal (D1) and having a center section extending in the direction of said first diagonal in both directions from the intersection of said first and second diagonals and extending for a part of the length of the first diagonal, at least one supplementary cutter (7, 8) formed by said drillhead extending along a part of said second diagonal from the center section of said main cutter, said main cutter having a pair of radially outer sections (10, 11; 51, 52) extending radially outwardly along the first diagonal each from an opposite end of said center section, and said supplementary cutter projecting outwardly in the axial direction of said drill shaft beyond said outer sections of said main cutter.