Terry's patent 1908 (no.11804) coil friction type locknut

Terry's patent 1908 (no.11804) coil friction type locknut viz:- 1 nut 1" diam. in section with spring; 1 bolt and nut 1" diam. complete

This form of lock nut was patented by Mr. A. E. Terry in 1908. It locks itself on its bolt by means of a helical wire spring which is fitted in a recess formed in the upper part of the nut and is coiled round the thread. One end of the coil is secured in a hole in the nut while the other end is normally free. The nut may be easily screwed on, because the coil tends to unwind and thus frees the bolt, but, should the nut tend to unscrew, the coil will wind itself and securely grip the bolt thread. The lock is released by the insertion of a pin, through a hole, so as to push back the free end of the coil and prevent it from closing on the bolt. A complete bolt and nut, I in. diam., are shown, and also a sectioned nut with its coil.