How to Use a Cotter Pin

Cotter pin by Monroe

Cotter pins offer an easy and reliable way to hold metal rods in place. Also known as cotter keys, they consist of a single U-shaped piece of metal. The two tines are typically the same length or nearly the same length. After positioning the metal rod, you can a cotter pin through it. You’ll need to manually manipulate the cotter pin, however, to ensure that it doesn’t fall out.

Step #1) Insert the Cotter Pin

The first step to using a cotter pin is to insert it. As previously mentioned, cotter pins are designed for use in metal rods, such as shafts. If a metal rod has a hole at the end, it should support a cotter pin.

Simply take the cotter pin and place it through this hole. The two prong-like tines should slide through the hole. The closed loop at the top of the cotter pin will prevent it from falling all the way through the hole.

Step #2) Bend the Cotter Pin

Now it’s time to bend the cotter pin. Because they are made of strong metals, such as steel or bronze, you may struggle to bend the cotter pin with your fingers — and that’s okay. You can use any handheld tool to bend it, such as a pair of pliers.

Using your preferred tool, bend the cotter pin’s two tines in opposite directions. Rather than pointing straight down, the tines should point horizontally and away from each other. By bending the tines, the cotter pin won’t be able to fall out of the metal rod.

Step #3) Check to Ensure the Cotter Pin Is Secure

Lastly, you should check to ensure the cotter is secure. Grab the top of the cotter pin and gently pull it to see if it comes out of the metal rod. Assuming you bent the tines properly, it shouldn’t come out. If the cotter pin does, in fact, come out, you may need to bend the tines farther out or replace the cotter pin with a larger size.

Don’t Forget to Replace!

It’s important to note that cotter pins aren’t reusable. If you remove a cotter pin from a metal rod, you’ll need to replace it.

Removal requires straightening the cotter pin’s two tines so that they point back down. By doing so, however, you’ll weaken the tines. If you reuse the cotter pin in another metal rod, it may not offer a secure hold. The newly weakened tines may break, at which point the cotter pin will likely fall out of the metal rod.

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