Locking of Bolts.
Throughout the complete machine it is necessary to lock the nuts of the bolts, to prevent their gradual loosening under the vibration of the engine, and different methods of accomplishing this are in use. Undoubtedly the best form of lock is by the use of a castellated nut and split pin. By this method one can readily ascertain whether or no a bolt is locked, while by the withdrawal of the split pin the bolt may be taken out. A disadvantage is that its use entails considerable drilling, so that a modification consists of fitting castellated nuts to all bolts liable to removal for minor adjustments; while elsewhere the threaded portion of the bolt is left a little longer than the nut, and then riveted over. Although this reduces labour, it is a somewhat destructive method; and it is also difficult to determine the adequacy of the riveting. Another method consists of filing the bolt end flush with the nut, and then centre punching three or four dots in the joint between nut and bolt.
This method is neat, the removal of a bolt is easily effected, and the fact that it has been used in the construction of some fast scouting biplanes is proof of its effectiveness.
Other systems include the use of two nuts, of a single nut soldered to the bolt end, and the various patent lock-washers, which in this country are not greatly in vogue. The practice of re-running down the threads of bolts to ensure ease in the application of the nut is not to be recommended—that is, indiscriminately done. Unless the die is properly adjusted there is a possibility of too much thread being taken off; the result, an extremely slack nut, being detrimental to general reliability. The durability of an aeroplane in service is dependent upon the good workmanship effected in the smallest and most insignificant detail. Moreover, it should be remembered that the absence of a split pin may eventually result in disaster.