Stop nuts (self-locking) nuts come in two basic varieties;
elastic with a nylon insert or,
all-metal.
Both types are found on general aviation aircraft. When would you use the elastic and when would you use the all-metal type.
Stop nuts, or sometimes called 'nylocks', 'self-locking' nuts, or 'fiber nuts' create a "off-torque" that resists loosening. The elastic nut uses nylon and is temperature limited. Depending upon the type of nylon used, the maximum temperature is either 250 or 350 degrees F. So for higher temperature applications one would use the all-metal nut, which can be used up to 550 degrees F., or the silver plated ones up to 800 degrees F.
Can I use the all-metal instead of the nylon nut?
Yes, however, the nylon offers several advantages. Generally, nylon lock nut offers the following advantages:
Better locking effectiveness than steel.
Better capability of providing renewed locking action after removal and re-installation. All metal nuts yield and wear away after repeated usage, whereas nylon flows in the thread voids, grips and dampens vibration between the bolt and nut. Nylocks are more re-usable.
All-Metal lock nuts wear away the protective plating on the bolt threads and may cause increased corrosion.
