Fig. 448.
In [Fig. 445], for example, the wrench is shown in the position in which it will just engage the nut, and at the first movement it will move the nut to the position shown in [Fig. 446]. The wrench is then turned upside down and placed upon the nut as in [Fig. 447], and moved to the position shown in [Fig. 448], thus moving the nut the sixth part of a revolution, and bringing it to a position corresponding to that in [Fig. 445], except that it has moved the nut around to a distance equal to one of its sides. Since the wrench has been moved twice to move the nut this distance, and since there are six sides, it will take twelve movements to give the nut a full revolution, and, there being 360° in the circle, each movement will move the nut 30°, or one-twelfth of 360°, and one-half of this must be the angle of the gripping faces of the jaws to the body of the wrench. The width of the opening in the work to admit the wrench in such a case as in [Fig. 445] must be not less than 30°, plus the width of the wrench handle, at the radius of the outer corner of the opening.
In the case of wrenches for square nuts it is similarly obvious that when the nut makes one-eighth of a revolution its sides will stand in the same position to receive the wrench that the nut started from, and in one-eighth of a revolution there are 45°. As the wrench is applied twice to the same side of the nut, its jaws must stand at one half this angle (or 221⁄2°) to the handle.
Fig. 449.
