Method and apparatus for self-adjusting boring bar

Abstract

Method and apparatus for conducting boring of a series of spaced walls on a workpiece using a self-adjusting boring bar. The method comprises: (a) supporting a spindle in a rotationally fixed tubular housing to provide an assembly having an unsupported extremity adapted to extend throughout the series of walls, the support providing for independent rotary movement but conjoint axial movement of the spindle within such tubular housing, such spindle carrying a cutting tool to project beyond the tubular housing; (b) providing an angularly flexible joint in each of said spindle, such as complementary curvilinear splines on two mated ends of different portions of said spindles, and tubular housing, such as separate tubular housing sections coupled by a web; (c) advancing the cutting tool successively through the series of walls to machine the aligned openings and thereby causing the spindle and tubular housing to follow successively through such machined openings, said spindle and housing providing, during advancement to machine the second and successive walls of the series, (i) concentric macroalignment of the spindle within the tubular housing and macroalignment of the tubular housing within the walls of the openings, and (ii) a sense of microalignment of the housing within at least the previously machined; and (d) in response to a sensed micromisalignment of said spindle head, selectively imparting a microangular steering force to the tubular housing and thereby to the spindle to achieve the desired microalignment. The apparatus employs a split tubular housing with piezoelectric means for imparting microscale angular adjustments.