There are many different types of locking nuts available. Most of the time you use whatever is lying around in bins or garage drawers due to convenience. The problem is that there are different locking nuts for different fastening needs.
The most common term I hear is “lock nut”; this could refer to several different types of nuts but most of the time it is in reference to nylon insert locking nuts. Since there is very little room to place markings on them, many manufactures use colored nylon as their brand. Some are yellow, red, grey, white and so on. This nut is traditionally formed with an additional collar to accept the nylon ring material. It is then staked by six evenly crimped impressions. This type is generally indicative of a grade 2 nut. The other way of determining grade is the notched markings on the hex corners. One notch identifies it as being grade 5 while 2 notches are grade 8. Some insert nuts are plated in clear, yellow or black zinc this does not refer to the grade even though the nuts we carry in grade 2 and 5 are clear zinc and our grade 8 are plated in yellow zinc. Since nylon is pliable, it does not damage male threads of bolts or studs with initial or repeated use by hand or power tools. However, as with all standard nuts, the increased friction between the nut and bolt thread will decrease the clamp load when the nylon is reused. Generally the nylon nut will not back off, but the joint clamp load is greatly diminished. We often recommend replacing nylon nuts on areas that have rotating mass or areas of severe on and off usage.
