Method for constructing a multiple segment rock bit

摘要

The cone cutter of each segment of a multi-segment rock bit is assembled onto its segment. A pin end of the segment is supported by an index pin and axially constrained in the direction away from the cone cutter. The cone cutter is clamped against and dimensionally indexed on a cone saddle having a circular surface of a diameter corresponding to the gage diameter of the completed rock bit. The cone is loaded in a direction axially of the segment in a manner to simulate the loading of the hole bottom that is to be drilled by the rock bit. The segment away from the cone is also loaded radially of the axis of the segment to take up tolerances along the axis of rotation of the cone cutter. The constraint of the cone and loading of the segment simulate the hole wall force on the cone experienced at the gage row and takes up tolerances radially of the axis of rotation of the cone along a line to the gage row in contact with formation material. A bridge prevents rotation of the segment about its lengthwise axis. With the setting of all constraints, a clamp at the pin end of the segment locks the segment in place and the bridge is removed. The included angle between faying surfaces of the segment is then finished. Thereafter, enough finished segments to make a complete rock bit are assembled and welded together along their faying surfaces. The action of axial and radial loading of the cone in a manner to simulate drilling loading prior to finishing the segments assures that the cone axis, offset, and gage diameter are all proper in an assembled rock bit.