Locking Clamp

The popular Vise-Grip tools are based on a clever locking clamp mechanism. The variation shown here is for a hold-down jig that holds a workpiece firmly to a surface. When joint A is pressed towards B, hold-down C moves down towards the work surface, holding an object placed at C. The ingeniousness of the device lies in the unique aspect that pressure at C increases virtually to infinity as the joint at A straightens. Joint A then passes just slightly beyond being straight and stops against the small bump below B, releasing some pressure at C and locking into position.

The Vise Grip locking pliers was invented by a Danish blacksmith, William Petersen. He realized his job would be a lot easier if he had a set of pliers that would clamp down and hold the piece of metal he was working on "in a vise-like grip." He built several prototypes, first out of cardboard and then wood. Finally, he hammered one out of metal on his forge. He got his first patent for a primitive version in 1921. He built an inventory and starting selling the Vise-Grip Pliers out of the trunk of his car to farmers and mechanics in the surrounding towns.