Plano-milling machine

Claim 1

A plano-milling machine comprising a horizontal table over which workpieces are movable in a first, "X axis" direction, a bridge over the table, a saddle movable along the bridge in a second, horizontal "Y axis" direction at right-angles to said first direction, a slide vertically movable in a third, vertical, "Z axis" direction relative to the saddle, a head carried by the lower end of the slide and having collet spindles arranged with their respective axes of rotation perpendicularly related and interconnected to be commonly driven, the head being mounted in the machine to be displaceable in the direction of the axis of rotation of one of said collet spindles and at right-angles thereto with the attitude of said one spindle axis remaining constant and the head being rotatable relative to the slide about the "Z axis" whereby a tool held by a horizontal arbor of the head may be presented to different vertical surfaces of a workpiece on the table, a combined indexing mechanism and bearing whereby the slide rotatably supports the head, said combined indexing mechanism and bearing comprising relatively rotatable annular upper and lower portions through which drive means for a vertical spindle of the head passes, and angularly-spaced guides in which a vertically movable wedge member is selectively engageable to lock the two portions of the bearing against relative rotation when in a chosen angular relationship, said indexing mechanism comprising means for introducing fluid under pressure to a part-annular chamber between said bearing portions on one side or the other of a vane in the chamber fixed relative to the head, and proximity switches to cut off the supply of pressurised fluid when a selected one of said guides is aligned with said wedge member.