US Patent 7465133 Toolholder with retractable bushing

An apparatus and method for machining a workpiece in a single-pass comprising a tool configured to produce a borehole when rotated and translated relative to the workpiece, a toolholder configured to fixedly secure and rotate the tool, and a bushing retractably coupled to the toolholder, so as to be shiftable between extended and fully retracted positions, and preferably biased towards the extended position, wherein said tool, toolholder, and bushing are cooperatively configured such that the bushing provides lateral support for the tool during the machining process.