Abstract: An earth boring drill bit, particularly for large diameter shafts, has a cutter assembly with improved bearing and seal arrangement and an improved cutting insert arrangement. A cutter assembly has an axle with an enlarged central portion and reduced portions on both sides. A cutter sleeve is carried on bearings by the central portion of the axle. An annular member with a central bore is secured to each side of the cutter sleeve. A metal face seal is secured between the reduced portion and the central bore on each side. The cutter contains rows of hard metal inserts secured in holes in the exterior. To reduce tracking, the inserts within a row are separable into groups with varied pitch within each group. The groups cycle with two groups having a gradual increase in pitch and two groups having decreasing pitch.

Abstract: An earth boring drill bit for large diameter shafts has an improved cutter arrangement. The drill bit has a cutter support member with a number of cutters mounted to it for disintegrating the earth formation face. At least one inner cutter is mounted near the center for cutting the center area. A number of gage cutters are mounted at the periphery to cut the gage area of the shaft. A number of intermediate cutters are spaced between the inner and gage cutters. Each intermediate cutter overlaps one-half of its width with an adjacent intermediate cutter.