Pulleys, gears, cranks, and other pieces are fastened to shafts by means of keys, the usual form being shown in Fig. 14. Keys, in their several forms, prevent the piece from turning other than with the shaft, and to some extent offer resistance to lateral movement along the shaft. For light pulleys, and pieces carrying only a small load, the saddle key shown in Fig. 15, may be used. As it conforms to the shape of the shaft, friction only prevents movement on the shaft. It is much used for temporary fastenings, where cutting the shaft is objectionable. The flat key shown at B, Fig. 15 is more secure than the other, yet requires but little metal to be removed from the shaft. The sunk keys shown at C, Fig. 15, is the one used for permanent fastenings, and is much the strongest and most satisfactory of the three. It fits a slot cut in both shaft and piece, has a slight taper so as to hold firmly when in place, yet admitting removal without difficulty, when necessary.

A taper pin, sometimes used in place of a key, is shown in D Fig. 15. Its more particular use is that of fastening cranks to their shafts.

A cotter is a tapering bar used for connecting two pieces, in such a way as to resist tension. A simple form is that shown at A, Fig. 16; the cotter resists tension while the collar on the rod also resists thrust. The form shown at B resists tension only, but has gib ends to prevent movement from place. A divided cotter is shown at G; the upper part should be shown with overlapping ends and is called a gib; the other is a plain cotter. An ordinary foundation bolt with iron washer is shown at D), Fig. 16, the gib ends keepig the cotter in place. Cotters are often used to connect two rods by means of overlapping straps as shownin Fig . 17. When, owing to vibration or. other causes, it becomes necessary to ensure that the cotter will be securely fastened, an arrangement of gib and cotter is used as shown in Fig. 18, the gib having shoulders and the cotter, which passes through the gib, fastened with a screw-bolt.

One view of a knuckle is shown in Fig. 19; these being used to connect rods which, for various reasons, cannot be fitted with a rigid joint. An adjustable joint is shown in Fig. 22, each end of the long nut being threaded, one end with a right hand thread and the other with a left hand thread. The central portion is without threads and enlarged to clear the ends of the rods. The outside is usually hexagonal, to which wrenches are applied for adjusting.

A flange coupling is shown in Fig. 20, each flange being keyed to the shaft with a sunk key. A hanger for shafting is shown in Fig. 21, one half giving a front view and the other half a cross section view. This is a common method for drafting any piece which is alike on both sides, a considerable saving in time and number of drawings being affected thereby. It must be understood by the reader that the exercises given in this series are but a few of the many forms of devices in use, but they well serve to give a general idea, which the reader can study in greater detail as occasion may require. The studies in Fig. 16 are sectioned and shaded to show the greater clearness given to drawings by such work.