Abstract: A workpiece (1) is fixed by means of a chuck (4) and rotates with a spindle (3) in a headstock (2). A first cam (30) is fixed to the main shaft of the spindle. Its control surface guides a feeler roller (31). A rotary pulse generator (8) is actuated by the rotation of the spindle shaft. An auxiliary motor (10) is disposed on a cross-slide (12) and causes an auxiliary shaft (21) to rotate. The pulse generator produces synchronization between the spindle shaft and the auxiliary shaft. The latter bears a second cam. According to the position of the cross-slide, the exact location of teh tools (16, 17) is determined by the first cam or by the second.

Abstract: The pedestal of the accessory apparatus, to be secured to the cross-slide of an automatic lathe, has a sliding guide arrangement for a bearing box in which a rotor is hydrostatically mounted for rotational and longitudinal movement. The rotor is held by a spring with its hydrostatically supported feeler-roll against a control curve which is accommodated encased in the bearing box. The rotor is connected by a sliding key connection to a key shaft seated fast on the shaft of an electric motor secured to the bearing box. The rotor is equipped at its front end with a slide plate guided for radial displacement, to which two diametrically opposite tools are secured. With one of these tools, an outside cylindrical surface adjoining a shoulder is machined on a non-rotating workpiece, whereupon the workpeice is rotated through 180.degree. so that the shoulder can be machined with the aid of the other tool, the slide plate being radially displaced on the rotor until it reaches a stop position.