Fig. 450.
Fig. 451.
When a nut is in such a position that it can only be operated upon from the direction of and in a line with the axis of the bolt, a box wrench such as shown in [Fig. 449], is employed, the cavity at b fitting over the bolt head; but if there is no room to admit the cross handle, a hub or boss is employed instead, and this hub is pierced with four radial holes into which the point of a round lever may be inserted to turn the wrench. Adjustable wrenches that may be opened and closed to suit the varying sizes of nuts are represented in [Figs. 450], [451], and [452]. In [Fig. 450], a is the fixed jaw solid upon the square or rectangular bar e, and passing through the wooden handle d. b is a sliding jaw embracing e, and operated thereon by the screw c, whose head is serrated to afford a good finger grip. Various modifications of this form of wrench are made; thus, for example, in [Fig. 451] a is the jaw, b a slotted shank, c the handle, all made in one piece. d is the movable jaw having a sleeve extension d′, and recesses which permit the jaw to slide on the shank longitudinally, but which prevent it from turning. The movable jaw is run to and from the nut or bolt head to be turned, by means of the screw g.
Fig. 452.
In another class of adjustable wrench the jaws slide one within the other; thus in [Fig. 452], the fixed jaw of the wrench forms a part of the handle, and is hollowed out and slotted to receive the stem of the loose jaw, which plays therein, being guided by ribs in the slot, which take into grooves in the stem of the loose jaw. A screw with a milled head and a grooved neck serves to propel the loose jaw, being stopped from moving longitudinally by a partly open fixed collar on the fixed jaw, which admits the screw and engages the grooved neck of the same. The threaded extremity of the screw engages a female screw in the loose jaw, and while the same are engaged the screw cannot be released from the embrace of the fixed collar, as it requires considerable lateral movement to accomplish this.