Lock nuts come in a wide variety of grades and styles. Examples of grades for lock nuts are A, B, C, 2, 5, & 8. Lock nuts are made by many manufacturers. Finding the best lock nut for your application can be difficult. The earliest method of a locking nut was the Hex Jam Nut. The jam nut was tightened against a surface and a heavy hex nut was tightened against the jam nut to keep it from loosening. K-Lock Nuts or Keps Nuts are lock nuts with a free-spinning external tooth lock washer attached to the nut. The locking action occurs when the teeth of the washer dig into the bearing surface. Serrated hex flange nuts act as a locking nut. The serrations are angled so that the keep the nut from rotating in a direction that would loosen the nut. These serrations increase the holding power of the nut by avoiding vibration. Another group of lock nuts are prevailing torque lock nuts. These nuts require a specific amount of torque to tighten because the nuts are designed to resist vibration. There are two types of resistance created by prevailing torque lock nuts. The first, and most common, is a plastic insert. In a nylon insert stop nut, or nylock nut, the plastic insert is made of nylon. When the threads of the bolt reach the nylon insert, the friction fit creates a tightness that resists vibration loosening. The nylon will deteriorate at 200 -250 degrees Fahrenheit. The second style of prevailing torque lock nuts is a non-circular head. The nut is deformed to be non-circular, making it nearly impossible to thread the nut onto a bolt without a wrench. This deformity creates a tight, vibration resistant assembly. Lock Nuts come in a variety of finishes. Plain finish, zinc plated, yellow zinc plated and hot-dipped galvanized are most common. Use Hot-Dipped Galvanized Lock Nuts with Hot Dipped Galvanized Bolts ONLY because the threads of the lock nut are tapped oversized to account for the heavy galvanized coating on the bolt. Be sure to match the grade & finish of your lock nut with the bolt for a proper assembly.
Most fastener items are available loose by the pound at your local Joseph Fazzio's store.