Abstract: This invention relates to an improvement for an adjustable open end wrench of the type comprising a stationary jaw and a movable jaw having a rack gear coupled thereto. A helical gear is coupled between the rack gear and the stationary jaw for driving the movable jaw toward and away from the stationary jaw. The rotational axis of the helical gear is oriented at an acute angle with respect to the longitudinal axis of the rack gear and the direction of motion of the movable jaw. This acute angle is substantially equal to the pitch axis of the helical gear teeth, whereby tangential sections of the helical gear teeth which are in sliding communication with the rack gear teeth are substantially perpendicular to the direction of motion of the movable jaw.