Abstract: In a micrometer head for an instrument for measuring internal dimensions there is included a casing in which at least one measurement contact piece having an inclined base is radially mounted in a slot or groove. The contact piece is driven by the axial displacement of a measuring cone and is maintained in contact with the inclined lateral surface of the cone by means of a return member. The axial displacement of the measuring cone, the base of which is guided in an axial cylindrical recess of the casing, is effected by the thrust of a spindle which has a micrometer screw mounted thereon, the screw being engaged in a threaded member connected to the casing. The cone and spindle have coaxial axes of rotation, and the cone, spindle and micrometer screw are so arranged that the path of movement of the inclined base of the contact piece on the cone is in the form of a tapered ramp having a long length and shallow inclination, the movement being caused by the combined axial and rotational movement of the cone.

Abstract: A measurement instrument in the form of a plug gage comprises a tubular body within which there is centered an axially movable rod, one end of which is intended to transmit the axial movements of said rod to a transducer system connected to the tubular body, while the other end thereof bears a conical part coaxial with said rod, with the lateral surfaces of the conical part resting against radially movable feeler balls, each of which is housed in a guide channel transverse to the longitudinal axis of the tubular body. The plug gage is characterized in that the tubular body bears over at least a portion of its length a coaxial centering sleeve which is removable and interchangeable, this sleeve being provided with transverse openings intended to permit the passage of the balls.