A split pin, also known as a cotter pin, or cotter key in the US, is a metal

fastener A fastener (US English) or fastening (UK English) is a hardware device that mechanically joins or affixes two or more objects together. In general, fasteners are used to create non-permanent joints; that is, joints that can be removed or disman ...

with two tines that are bent during installation, similar to a staple or

rivet A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylinder (geometry), cylindrical shaft with a head on one end. The end opposite the head is called the ''tail''. On installation, the deformed e ...

. Typically made of thick

wire file:Sample cross-section of high tension power (pylon) line.jpg, Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample d ...

with a half-circular cross section, split pins come in multiple sizes and types. The British definition of "cotter pin" may include the equivalent to US term " cotter". To avoid confusion, the term split cotter is sometimes used for a split pin. A further use of the term "cotter pin" is the "crank cotter pin" used to lock bicycle pedal cranks to the bottom bracket axle. These are not "split" at all and are wedge shaped.

History

The cotter pin was invented by Ira J. Young of the Wire Manufacturing Company in

St. Louis, Missouri St. Louis ( , sometimes referred to as St. Louis City, Saint Louis or STL) is an Independent city (United States), independent city in the U.S. state of Missouri. It lies near the confluence of the Mississippi River, Mississippi and the Miss ...

in 1912. He filed two patents for machines to make the fastener that year.

Construction

A new split pin (see figure A) has its flat inner surfaces touching for most of its length so that it appears to be a split cylinder (figure D). Once inserted, the two ends of the pin are bent apart, locking it in place (figure B). When they are removed they are supposed to be discarded and replaced, because of

fatigue Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself. Fatigue (in the medical sense) is sometimes associated wit ...

from bending. Split pins are typically made of soft metal, making them easy to install and remove, but also making it inadvisable to use them to resist strong shear forces. Common materials include

mild steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, cobalt ...

brass Brass is an alloy of copper and zinc, in proportions which can be varied to achieve different colours and mechanical, electrical, acoustic and chemical properties, but copper typically has the larger proportion, generally copper and zinc. I ...

bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals (such as phosphorus) or metalloid ...

stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...

, and

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

Types

The most common type of split pin is the extended prong with a square cut, but extended prongs are available with all of the other types of ends. The extended prong type is popular because the difference in length of the two tines makes it easier to separate them. To ease insertion into a hole the longer tine may be slightly curved to overlap the tip of the shorter tine or it is beveled. ''Hammer lock'' split pins are properly installed by striking the head with a hammer to secure the pin. This forces the shorter tine forward, spreading the pin.. Types include ''standard'', ''humped'' and ''clinch''.

Sizes

The diameters of split pins are standardized. American split pins start at in and end at in. Metric conversions in the table below are approximate.

Applications

Split pins are frequently used to secure other fasteners, e.g.

clevis pin A clevis fastener is a two-piece fastener system consisting of a ''clevis'' and a ''clevis pin head''. Terms The ''clevis'' is a U-shaped piece that has holes at the end of the prongs to accept the clevis pin. The ''clevis pin'' is similar to a ...

s, or to secure a castellated nut,. or, infrequently, as a low-tech

shear pin A shear pin is a mechanical detail designed to allow a specific outcome to occur once a predetermined force is applied. It can either function as a safeguard designed to break to protect other parts, or as a conditional operator that will not al ...

. Split pins are cheaper but less reusable than linchpins, and provide less strength but easier to install/remove than

spring pin A spring pin (also called tension pin or roll pin) is a mechanical fastener that secures the position of two or more parts of a machine relative to each other. Spring pins have a body diameter which is larger than the diameter of the hole they a ...

References

Notes Bibliography *. *. *. *.

External links

* {{Authority control Fasteners Mechanical fasteners Metallic objects