Fig. 432.
Fig. 433.
In cases where nuts are placed under rapid vibration or motion they are sometimes detained in their places by pins or cotters. The simplest form of pin used for this purpose is the split pin, shown in [Fig. 431]. It is made from half round wire and is parallel, and does not, therefore, possess the capability of being tightened when the nut has become loosened from wear. As the wire from which these pins are made is not usually a full half circle the pins should, if the best results are to be obtained, be filed to fit the hole, and in doing this, care should be taken to have the pin bear fully in the direction of the split which is longitudinal to the bolt, as shown in [Fig. 432], where the pin is shown with its ends opened out as is required to prevent the pin from coming out. If the pin bears in a direction across the bolt as at a d, in [Fig. 433], it will soon become loose.
Fig. 434.
Pins of this class are sometimes passed through the nut itself as well as through the bolt; but when this is the case, there is the objection that the nut cannot be screwed up to take up any wear, because in that case the hole in the nut would not come fair with that in the bolt, and the pin could not be inserted. When, therefore, such a pin passes through the nut, lost motion must be taken up by placing an additional or a thicker washer behind the nut. The efficiency of this pin as a locking device is much increased by passing it through the nut, because its bearing, and, therefore, wearing area, is increased, and the pin is prevented from bending after the manner shown in [Fig. 434], as it is apt to do under excessive wear, with the result that the end pressure of the nut almost shears or severs the pin close to the perimeter of the bolt.