Raise drill bit inboard cutter assembly

A roller cutter comprising:

• a hanger bracket including a major section having first and second end portions, and a shoulder section extending transversely from said first end portion of said major section, said shoulder section having portions defining a groove open in the direction toward said second end portion of said bracket major section, said major section having a thrust surface located adjacent said second end portion;
• a spindle extending transversely outwardly from said bracket major section in a direction opposite to said shoulder section;
• and
• roller means antifrictionally mounted on said spindle to rotate about said spindle.

A raise bit for enlarging a preformed pilot hole into a larger diameter by disintegrating the earth formations surrounding the pilot hole, the bit having a cutter carrier frame and a drive stem extending upwardly from the cutter carrier frame and into the pilot hole, the improvement comprising:

• a plurality of cutter housings disposed about the cutter carrier frame at locations spaced radially outwardly from the drive stem, at least some of said housings including an upright wall extending generally upwardly from the cutter carrier frame, said upright wall having an elongate upper edge portion, a first roller cutter retaining wall extending transversely outwardly from an upper portion of said upright wall at an orientation obliquely to the plane of said upright wall, and a second roller cutter retaining wall spaced below and parallel to said first roller cutter retaining wall, said two roller cutter retaining walls having aligned arcuate recesses formed therein;
• a central roller cutter assembly mounted on a corresponding cutter housing to extend in a direction generally toward the stem, each of said central roller cutter assemblies including;
• a hanger bracket having an upright section including upper and lower end portions, a shoulder section extending transversely outwardly from the upper end portion of said upright section, said shoulder section having portions defining an elongate, downwardly open groove extending parallel to the plane of said upright section for receiving the upper edge portion of said cutter housing upright wall;
• a spindle cantilevered outwardly from said hanger bracket upright section in a direction opposite to said shoulder section;
• and
• roller means antifrictionally mounted on said spindle to rotate about said spindle;
• and
• securing means for detachably securing each of said central roller cutter assemblies to a corresponding cutter housing by simultaneously forcing said hanger bracket groove downwardly against the upper edge portion of a corresponding housing upright wall and loading the lower end portion of said hanger bracket upright section against said housing upright wall.