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A lock bolt is a two-piece metal fastener consisting of a round collar and a cylinder with segmented threads. A fastener is something used to join two surfaces and keep them together. A lock bolt is secured when the collar is threaded onto the cylinder and pressed into place using a powerful crimping tool. Lock bolts are commonly used to create secure long-term connections that are capable of withstanding force and vibration. Machinists will often choose to use a lock bolt to securely connect two surfaces when welding is impossible or impractical.
The quick assembly, inexpensive nature and comparative safety of lock bolts makes them a practical fastener option for almost any application. Locking bolts generally provide similar strength and durability to more dangerous, hot-fastening alternatives such as riveting and spot welding without the possibility of heat damage or the high equipment and training costs. An easy-to-install, practical heavy-duty lock bolt can stay strong and function for many years, even under harsh weather conditions. Some lock bolt collars can be removed after installation so the cylinder can be reused with a new collar on another project.
Lock bolts are often designed to have high tensile and shear strength in order to provide optimal structural integrity. Shear strength refers to the capability of a fastener to hold surfaces together with weight loads applied in multiple directions. Tensile strength is the ability of the material the lock bolt is made of to stay in one piece despite the applied pressures. The integrity of the material and lock connection make machinery lock bolts reliable connectors.
Traditional bolts usually loosen due to vibration. Movement between two connected surfaces may cause a threaded fastener to slowly spin apart and separate. Even a small amount of separation in a fastener lowers the shear strength of the connection. To deal with this problem, some builders use a secured lock bolt, which is capable of withstanding vibration without any loosening or weakening the connected structure.
Pneumatic-hydraulic and hand-powered lock bolt fastening tools, often called riveters, are available at most hardware stores. Riveters and power riveters are the tools used to squeeze, or "swag," the soft metal collar onto the bolt to secure the lock. Some riveters have a built-in feature that breaks off the extra length of the threaded cylinder once the collar has been swagged onto the bolt. The pneumatic-hydraulic riveting tools are a bit louder than the hand powered tools, but they work much faster and generally have more uniform results.