A ferrule is a small metal collar used at a termination or join in wiring to crimp and gather the wires. These devices are used in the construction of a number of electrical components, such as circuit boards, and can also be used in various wiring projects. Suppliers of electrical components often stock a range of ferrules in different sizes and styles for different projects. Customers may also be able to special order custom products for particular types of products, although a manufacturer may require a larger order.
The ferrule takes the form of a short wire tube, which may have a flared base in some cases. To use it, an electrician or technician slides it over the involved wires and crimps it, clamping the wires together. A crimping tool can be used for this, or the technician can use heavy pliers or clamps. The technician can insert the end of the ferrule into a contact point to connect wiring, or the ferrule can create a terminus of a wire or lead, depending on the setting.
Some ferrules come insulated with rubber, plastic, or other materials. These may be color-coded for convenience. Operators can use color coding to help them properly connect contacts, or to code specific types of wires. The insulation may come in the form of a removable band so the operator can pick the color for a given application. Uninsulated ferrules are left bare.
For the purposes of automation, it is possible to buy ferrules yoked together in bandoliers that can be fed into manufacturing equipment. The equipment makes the connections, clamping them automatically as the wiring moves down the assembly line. A technician may check the quality of the connections and look for signs of wear or improper crimping, but does not perform the work by hand. Automation can speed the production process of many electrical components.
Ferrules can be particularly useful for wiring connections into larger circuits and devices. While it is possible to bring the wires into contact directly, they can be subject to breakage and strain. The ferrule creates a protective cover that will limit the stress at the wiring point, making problems with the system less likely in the future. The wire is also not forced to bend or twist in a way that could predispose it to cracking and failing in the event of pull or strains from the other end.