Self-locking nuts

Special care should be exercised in systems where previous experience has indicated tray vibration problems. When tray vibration is expected, bolted-through tray connections should be used, along with lock washers or self-locking nuts, rather than frictional fastening. 

Figure 12.8. Locking nuts (a) standard lock nut (b) slotted and castle nuts (c) Nyloc nut(d) Aerotight nut(e) Philidas self-locking nut (f) torque lock nut...

Self-locking nuts are available which are easy to assemble and do not require a hole in the bolt or the use of a split pin. One type, known as a Nyloc nut. Fig. 12.8(c), incorporates a nylon insert round the inner top end of the nut. As the nut is screwed on, the nylon yields and forms a thread, creating high friction and resistance to loosening. 

A third type, known as a Philidas self-locking nut, Fig. 12.8(e), has a reduced diameter above the hexagon. Two slots are cut opposite each other in the reduced diameter and the metal above the slots is pushed down, which upsets the thread pitch. When screwed in position, the thread is gripped hy the upset portion, preventing the nut from working loose. 

Use the inner hexagon spanner to fix the ball pin remove the self-locking nut. 

Support the lower arm by jack use the inner hexagon spanner to fix the ball pin and tighten the self-locking nut to specified torque. Tightening force 63 + 5N m... 

PTFE has also been used in some expl nuts, where a PTFE insert provides a self-locking feature of the thread and a gas-tight seal between thread segments, bolt and housing (Ref 5). It has also been used to make inert seals or containers for pyrot compns (Ref 1)... 

Parts shall be adequately secured so that should any wire, washer, spring, screw, nut, or similar part fall out of position or come loose, it cannot reduce the distances over the reinforced or supplementary insulation levels specified in the standards. As mentioned, parts fixed in place by screws or nuts with self-locking washers or other means are not liable to come loose, and soldered wires are not considered adequately fixed unless they are held in place near the termination independently of the soldered connection. 

Lemma 7.4. The equilibrium point of the linear system described by (7.18) is stable when the force is applied in the direction of the nut translation and the lead screw drive is not self-locking, i.e., RQ. > 0 and p < tan 2. 

Thread locking. The first applications for anaerobic adhesives were for locking threaded fasteners. Filling the inner space between a nut and bolt with a hard, dense material prevents self-loosening. 

The cost of riveting is lower than that of most other methods of fastening, due to the absence of plain washers, locking washers, nuts or split pins also, the use of self-piercing rivets eliminates the need to predrill holes. Rivets are available in steel, brass, copper and aluminium in a variety of types. The more standard head types used are shown in Fig. 12.11. 

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