Abstract: A caliper has an elongated beam provided with at least one longitudinally extending rack. A slider displaceable longitudinally along the beam has a mechanism holder which is pivoted on the slider about a transverse pivot axis. An arbor is rotatable in journals formed in the front and rear sides of the mechanism holder about an arbor axis pivotal to and offset from the pivot axis. A pinion on the rear end of this arbor meshes with the rack so that displacement of the slider along the beam rotates the arbor. A scale carried on the slider cooperates with a pointer carried on the front end of the arbor for indicating the relative positions of the slider and the beam. A spring carried on the slider bears on the holder and urges the holder in a direction so as to force the pinion into good mesh with the rack.