Abstract: The spindle supporting head of a multiple spindle screw machine is intermittently rotated to place its spindles into successively different angular positions about the axis of a spindle drive shaft which extends coaxially into the center of the head. When each spindle is rotatably indexed into a particular angular position, a piece of bar stock is fed through the spindle and projects beyond one end thereof. Each of a plurality of tool slides, which are mounted adjacent the end of the head from which the spindle projects, carries a tool which registers with the stock projecting from an adjacent spindle. The slides are connected to servo motors which are operable by an associated computer to move their tools toward and away from the stock projecting from the associated spindles. Normally the head is secured against rotation by a hirth ring which intermittently is moved from its locking position to release the head so that it can be rotatably indexed.

Abstract: In an automatic screw machine two spindles are mounted coaxially one within the other and are keyed together for rotation in unison in the indexing head of the machine. The inner spindle has a collet on one end thereof; the outer spindle is shiftable axially relative to the inner spindle between collet opening and closing positions. A spring, which surrounds the inner spindle at one end thereof, urges a washer on the inner spindle against one end of the outer spindle normally to urge the outer spindle resiliently into a collet closing position. A hydraulic cylinder, which surrounds the outer spindle at the side of washer remote from the spring, contains a piston which is engaged at one side with the washer and at its opposite side communicates with a fluid pressure chamber. To open the collet pressure is applied to the fluid in the chamber, thereby causing the piston to compress the spring and to permit the outer spindle to move to a collet opening position.

Abstract: A pair of spindles are journaled coaxially one within the other in the indexing head of an automatic screw machine, and with the outer spindle disposed to be reciprocated axially between first and second limit positions in which it opens and closes, respectively, a collet which is supported by the inner spindle in the bore of the outer spindle. The outer spindle is urged axially to a collet closing position by a compression spring; and a camming element is rotatably adjustable about the outer spindle between a first position in which it urges the outer spindle axially rearwardly against the resistance of the spring to open the collet, and a second position in which it permits the spring to return the outer spindle to a collet closing position. The spring tension is adjustable by another element which is threaded on the outer spindle.