Abstract: A tool designed to operate in a substantially vertical position without contact with a workpiece such as a laser beam machining head comprising an operating member and a support for this member rigidly connected to a machine frame. This operating member comprises mounting means resting at at least three points on a support, this tool also has abutment means impeding displacement of the operating member in a plane substantially perpendicular to its axis (W, W').

Abstract: The tracer head comprises a casing, an axially movable tracer and a radially movable tracer. The radially movable tracer comprises a ball head, a feeler disc and a stem connecting the ball head with the feeler disc. The ball head has the form of a ball zone, the lower flat surface of which rests on the bottom surface of the casing when the radially movable tracer is in its inoperative position. The upper surface of the ball head is a contact surface with the axially movable tracer. The ball-like circumference surface of the ball head lies free of play on the inside wall of the casing. The stem passes with a certain amount of play through a bore provided in the bottom of the casing. The axially movable tracer contacts the upper flat surface of the ball head always only in one point. By means of this a precise transfer of the tilting movements of the radially movable tracer is secured. The tracer head has a substantially smaller diameter than the known tracer heads.