BORING HEAD OF CENTERLESS LATHE

摘要

A shaving machine for tubular or rod-like workpieces has a tubular tool holder which is rotatable in two axially spaced main antifriction bearings installed in the machine frame. An auxiliary antifriction bearing surrounds the tool holder between the two main bearings and its inner race is coupled by rods with a sleeve which is movable axially of the tool holder in the region of one main bearing. The sleeve has a conical internal surface abutting against complementary conical surfaces of several equidistant supports for shaving tools which are caused to move radially in response to axial movement of the sleeve. The outer race of the auxiliary bearing carries several nuts which mesh with axially parallel feed screws mounted in the machine frame and coupled to each other for simultaneous angular movement by means of pinions provided on the feed screws and meshing with an internal gear which is rotatable in the frame. A reversible electric motor can be drivingly connected with a gear on one of the feed screws by way of either one of two gear trains which can rotate the one feed screw at different speeds. As the one feed screw rotates in the frame, it causes the other feed screws to rotate to the same extent and in the same direction to thereby move the outer race of the auxiliary bearing axially of the tool holder. The outer race shifts the inner race which changes the axial position of the supports for shaving tools so that the tools move radially outwardly or inwardly.