Fig. 435.
To enable the pin to take up the wear, it is a good plan to file on it a flat place, which must be parallel to the sides of the pin-head and placed against the nut-face. The hole in the bolt is in this case made to fall slightly under the nut, as in [Fig. 435], so that the flat place is necessary to enable the pin to enter. By filing the flat place taper, the lost motion that may ensue from wear may be taken up by simply driving the pin in farther.
Fig. 436.
In place of this class of split pin, solid taper pins are sometimes used, but these, if employed in situations where they are subject to jar and vibration, are apt sometimes to come loose, especially if they be given much taper, because in that case they do not wedge so tightly in the hole. But if a taper pin be made too nearly parallel, it will drive through too easily, and has less capability to take up the play due to wear. An ordinary degree of taper is about 5⁄8 inch per foot of length, but in long pins having ample bearing area, 1⁄2 inch per foot of length is ample. To prevent taper pins from coming loose from vibration, they are sometimes forged split at the small end, as in [Fig. 436], and opened out at that end after the manner shown in [Fig. 432]. This forms a very secure locking device, and one easily applied. The split ends are closed by hammer blows to remove the pin, and it is found that such pins may be opened and closed many times without breaking, even though made of cast steel. The heads and ends are rounded so as to prevent them from swelling from the hammer blows necessary to drive them in and out. When a taper pin is passed through a nut and bolt, it simply serves as a locking device to secure the nut in position, and the lost motion due to wear must be taken up by the application of a washer beneath the nut, as already described. If, however, the taper pin be applied outside the nut, it may be made to take up the wear, by filing on it a flat place, and locating the hole in the bolt so that it will fall partly beneath the nut, as shown in [Fig. 435]. In this case, the nut may be screwed up to take up the wear, and the pin by being driven farther in will still bear against the nut and prevent its slacking back.
Fig. 437.