Fig. 461.
When a circular nut has its circumference provided with notches as was shown in [Fig. 412] the wrench is provided with a rectangular piece as shown in [Fig. 461]. This piece should slope in the direction of a for the reasons already explained with reference to the cylindrical pin in [Fig. 459]. It is obvious, however, that this wrench also may be made upon Professor Sweet’s plan, in which case the pin should be straight.
Keys and Keyways.—Keys and keyways are employed for two purposes—for locking permanently in a fixed position, and for locking and adjusting at the same time. Keys that simply permanently lock are usually simply embedded in the work, while those that adjust the parts and secure them in their adjusted position usually pass entirely through the work. The first are termed sunk keys and keyways, the latter adjusting keys and through keyways.
Fig. 462.
The usual forms of sunk keyways are as follows:—[Fig. 462] represents the common sunk key, the head h forming a gib for use in extracting the key, which is done by driving a wedge between the head and the hub of the work.