When piston 1 is moved to the right by the action of fluid delivered to the left end of its cylinder, gear rack 2, rigidly attached to the piston rod, turns pinions 3 which are attached to screws 4. Each screw 4 has two portions, one with right- and the other with left-hand thread, and the screws are constrained against axial movement. When the screws are rotated, V-block jaws 5 with internal right- and left-hand threads, mounted on the screws, move toward each other, locating and clamping round workpiece 6. To compensate for differences in diameter of workpiece 6, the torque is transmitted from pinion 3 to screw 4 in one of the two vises through a spiral spring (not shown).
$4027$THP,GC$