Nyloc nut
From Wikipedia, the free encyclopedia
A Nyloc nut, also known nylon insert lock nut, is a kind of nut that includes a ring of nylon inside the thread. It is designed to increase locking force and prevent the nut from coming loose. The internal nylon ring has no threads cut into it; it is forced to deform around the threads as the nut is twisted on, ensuring a tight grip on the thread. In most applications, this type of nut cannot be reused after being removed.
Nyloc is a registered trade name of Forest Fasteners.