Abstract: A fluid operated machine vise having a fixed jaw and a movable jaw. The movable jaw includes a hollow spindle threadedly engaged therewith so that upon rotation of the hollow spindle, the movable jaw will be moved toward and away from the fixed jaw. A fluid operated mechanical power amplifier is provided and is connected in association with the movable jaw so that upon application of force by the mechanical power amplifier to the movable jaw, forces greater than would be normally achieved are produced. A stop is provided for limiting the maximum clamping force. The stop limits the effective stroke length of the mechanical power amplifier.