What Is a Copper Duplex Ferrule?

Nomenclature

• The term “copper ferrule” is something of a misnomer; the word “ferrule” is derived from “ferrous” because for many centuries iron was the material typically used to make such metal objects. Duplex also has a Latinate derivation; it refers to the function of the ferrule in that it holds two items together. Duplex ferrules are also called “twin wire” ferrules.

Single Ferrules

• Aside from their use as fasteners at joints, ferrules are sometimes used for reinforcement; for instance, the small plastic or metal tubes at the ends of shoelaces -- properly called aglets -- are ferrules. While copper ferrules may be used to make the reinforcement more decorative, there is seldom a reason to use a duplex ferrule in this application.

Duplex Ferrules

• Duplex ferrules are circular or oval in shape, made of metal or -- less commonly -- plastic and used primarily as fasteners. Perhaps the most ubiquitous and highly visible use of duplex ferrules is in creating a loop in wire rope used for towing vehicles, fence-making and similar applications. The wire is typically looped around an eyelet-shaped guide, properly called a thimble, and locked into place by a ferrule where it doubles back on itself. Ferrules work well as locking devices at the joints of any fibrous, stranded, rope-like material, such as wires.

Usage

• Once the two objects to be joined are positioned, it is necessary to deform the ferrule to keep them in place. This can be done with a standard crimper and a specialized attachment device designed for the purpose or simply by hammering.

Copper Duplex Ferrules

• Copper single ferrules are used to make functional joints more decorative, such as the tips of high-end umbrellas and golf clubs. A duplex ferrule is a ferrule large enough to accommodate two objects that must be joined together; a copper duplex ferrule is no more than such a device manufactured from copper. Copper ferrules are typically used where electrical conductivity is an important consideration; all the strands of the wire that contact the ferrule must be able to conduct electricity. Further, in the crimping process copper ferrules deform more readily without heat than do iron ferrules. Resistance to corrosion can also be a factor, and copper does not rust.