science

Split pin

Split pin is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Split pin rather than just read about it. In short: A split pin, also known as a cotter pin, or cotter key in the US, is a metal fastener with two tines that are bent during installation, similar to a staple or rivet. Typically made of thick wire with a half-circular cross section, split pins come in multiple sizes and types.

Key takeaways

Split pin belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Split pin to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Split pin from memory before moving on to harder problems.

Reference excerpt

A split pin, also known as a cotter pin, or cotter key in the US, is a metal fastener with two tines that are bent during installation, similar to a staple or rivet. Typically made of thick wire 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 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 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, brass, bronze, stainless steel, and aluminium.

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 1⁄32 in and end at 3⁄4 in. Metric conversions in the table below are approximate.

Applications

Split pins are frequently used to secure other fasteners, e.g. clevis pins, or to secure a castellated nut, or, infrequently, as a low-tech shear pin. Split pins are cheaper but less reusable than linchpins, and provide less strength but easier to install/remove than spring pins. Cotter pins are also occasionally used to attach Cap badges to their respective headwear.

See also Cotter (pin) Circle cotter Hairpin clip Linchpin R-clip Spring pin

References Notes

Bibliography

External links Media related to Split cotter pins at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Split pin

Start with the simplest possible case. Write down what Split pin claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Split pin before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Split pin ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Split pin

In research: Split pin appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Split pin in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Split pin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fasteners, Metallic objects, so understanding it makes those chapters shorter.
In everyday life: Look for Split pin outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Split pin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Split pin means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Split pin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Split pin in simple terms?

Why does Split pin matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Split pin?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Split pin.