A ferrule (a corruption of Latin viriola "small bracelet," under the influence of ferrum "iron.") is a name for types of metal objects, generally used for fastening, joining, or reinforcement. They are often narrow circular rings of metal, or less commonly, plastic.
Most ferrules consist of a circular clamp used to hold together and attach fibers, wires or posts, generally by crimping, swaging, or otherwise deforming the ferrule to permanently tighten it onto the parts that it holds.
Examples of such ferrules:
- On a two-piece kayak paddle, the part that connects the two ends together.
- In a brush the ferrule binds the bristles or hair to the handle.
- On an ice axe, the metal spike at the end of the shaft
- The metal ring which is crimped to hold the eraser in place on pencils with an attached eraser
- The metal ring which holds a chisel blade's tang to the handle
- In fiber optic terminations, glass or plastic fibers are bonded to precision ferrules and polished for splitting or connecting two fibers together
- In restorative dentistry, margin of a cast crown that stabilizes root-canal treated teeth
- In golf, a plastic sleeve that adorns the bottom of most steel and graphite shafts just above the club head hosel. Originally designed to protect the shaft from damaging vibrations, it is now used mainly for aesthetic purposes
- In musical instruments, a metal band used to prevent the ends of wooden instruments from splitting. Also the semi-circular metal band that holds the fibers in place on the frogs of bows for violin family instruments.
- Compression fittings for attaching tubing (piping) commonly have ferrules in them.
- A swaged termination type for wire rope
- Cap at the end of a cane or umbrella.
- In pool and billiards, the portion of a cue that tops the shaft and to which the leather tip is bonded; historically made of ivory, now typically made of phenolic resin
- In fishing, the male and female joints that join one section of a rod to the next is known as the ferrule.
- In bicycles, a metal cap at the end of cable housing with a hole for the cable