Workpiece-measuring apparatus, in particular for grinding machines

workpiece-measuring apparatus, in particular for grinding machines, comprising:

• two arms (8) oscillatingly supported by fulcrums (9) and having respective work portions (8b),
• feelers (10) on said work portions (8b) for contacting a workpiece (3),
• sensors (11) for measuring oscillations of said arms (8) about said fulcrums (9),
• drive means for selectively exerting at least one contact force and at least one release force capable of rotating said work portions (8b) of said arms (8) respectively towards and away from said workpiece (3),
• wherein said drive means comprise:
• magnetic elements (14) carried by each of said arms (8), said magnetic elements (14) having active faces (14a) having opposite polarities,
• at least one magnet (13) having opposite polarities and located to cooperate with said active faces (14a) of said magnetic elements (14) to create magnetic forces between said at least one magnet (13) and said magnetic elements (14),
• means (15) for selectively reversing said polarities of said at least one magnet (13) relative to said polarities of said active faces (14a) of said magnetic elements (14) to thereby reverse the direction of said magnetic forces for selectively providing said at least one contact force and said at least one release force.