Toe clamp, screw type

When the user unscrews the square head bolt, the toe releases the work. Then the clamp retracts backwards and the work is removed from clamping position. A new work is placed in clamping position and the clamp is pulled forward. The user screws the bolt and clamps the work. The clamping force depends on toe dimensions and bolt size (force equilibrium).  The distance of thread hole from rotation center must be max double the distance of the cylindrical contact. Select a dowel pin with a double shear load five times the clamping force.