Piston counterboring machine

A machine for machining the solid outer end face of a piston so as to form in said end face an annular counterbore with an axially outwardly projecting central land at the center thereof comprising, a base, a headstock housing on said base having an axial bore therein, means for mounting a piston to be machined on said base so that the central axis of the piston is aligned with the axis of said bore, a carrier journalled for rotation in said bore, said carrier having an axially extending bore therein which is eccentric relative to the axis of rotation of the carrier, a spindle housing secured in the bore of the carrier to rotate therewith, said spindle housing being rotatably adjustable in said carrier bore, said spindle housing having an axially extending bore therein which is disposed eccentrically relative to the central axis of the spindle housing, a tool spindle journalled for rotation in said spindle housing bore and having a cutting tool thereon adapted to engage said end face of the piston when the piston and tool are displaced axially toward one another, means for moving the piston axially relative to the spindle, means for rotating the spindle around its own central axis and simultaneously rotating the carrier about the axis of the bore of the headstock housing so as to cause the rotating cutting tool to rotate about the axis of the spindle and to orbit around the central axis of the housing bore and thereby machine said counterbore, and said means for rotating the spindle having an electric motor which is fixed relative to said spindle housing, said motor having an output shaft operatively connected with said spindle, and drive means for rotating the carrier first in one direction through at least one revolution and then in the opposite direction through at least one revolution.