Abstract: A lead screw tapping unit is disclosed wherein a tap or thread forming die is mountable on a tool support spindle which is longitudinally movable with a nonrotatable quill. The spindle is rotatably driven by a reversible drive motor and has a lead screw carried thereon which cooperates with a lead nut to effect controlled inward feeding and withdrawal of the tap relative to a workpiece. The lead nut carries a cam bushing which is operative to actuate a safety switch and deenergize a drive motor to stop rotation of the spindle should the spindle and tap undergo a thrust overload condition, or if seizure occurs between the lead screw and lead nut.

Abstract: A machine tool unit is disclosed having a housing supporting a quill and rotatable tool support spindle for longitudinal movement under fluid pressure, and including control means disposed eccentrically of the quill and connected thereto so as to control axial feed movement of the quill without exerting a bending moment on the quill which would cause directional deviation of the quill and spindle during feed movement.