Cotter pins, while simple in design, are infinitely useful when you need to keep pieces of machinery in place and secure over a period of time. A cotter pin is a two-pronged fastener made from metal that installs easily while providing structural support.
FMW Fasteners offers both zinc-plated and stainless steel cotter pins. When you need cotter pins that are going to work hard each day, just like you do, find the toughest cotter pins available when you choose FMW Fasteners as your supplier.
What Are Cotter Pins?
Cotter pins, also known as split pins, are designed to hold bolts in place. These U-shaped pieces of metal with a wide circular top can be made from stainless steel or zinc and come in a range of sizes. There are also different styles of cotter pins available, from extended prong pins to R-shaped pins.
Uses for Cotter Pins
The primary use for a cotter pin is to secure a bolt by slipping into a hole drilled in the bolt body. Certain types of bolts are specifically designed for use with cotter pins and have pre-drilled holes for this purpose.
To attach a cotter pin to a compatible bolt, you simply slide it into the hole. Once the pin is all the way through the hole, you twist the ends of the pin outwards so that they pull away from each other. When the prongs of the pin are pulled well apart, they provide a stable hold and won't slip out.
Cotter pins are ideal for use with bolts intended for machinery that moves or vibrates. Some examples include:
- Fastening a nut on a motorcycle or vehicle wheel
- Securing a car hub
- Affixing a bolt to a motor
How to Choose the Right Size Cotter Pins
When choosing the right size of the cotter pin, there are two dimensions to consider. You want a pin that is long enough to reach all the way through the hole in the bolt with some left over for bending, but without so much extra length that it can't provide tension.
Additionally, the pin needs to be the right diameter to fit into the bolt's hole and yield a lasting hold. If it's too narrow, the pin will wobble and compromise the assembly's stability. FMW Fasteners offers 18 cotter pin sizes to choose from, including small cotter pins that measure only 1/32 of an inch. Our thickest pin measures 3/8 inches in width. Pin lengths range from ¼ inch to 6 inches.
When choosing the best cotter pin for your application, consider:
- Width: Measure the diameter of the hole where the cotter pin needs to fit, and find a pin in the biggest possible size to fit in the corresponding material hole.
- Head size: Find a cotter pin head size that is large enough to prevent the pin from moving over time with constant vibrations but no so large that it could prevent movement of other pieces or that it could become jammed.
- Length: Look at the length of the holes you need to secure and compare this number to the shortest leg of the cotter pin — the length of the hole should be shorter than both cotter pin prongs to ensure the cotter pin performs effectively and dependably. If you can’t find a cotter pin that fits the exact length requirements of your item, choose a larger-sized cotter pin and cut the materials down to the ideal size.
Zinc vs. Stainless Steel Cotter Pins
Whether you need zinc-plated or stainless steel pins depends on your project needs and budget. Stainless steel is often more durable and corrosion-resistant than zinc, but zinc is typically the more cost-effective option. If you're unsure which type of cotter pin is right for your needs, FMW Fasteners can help you compare the benefits and applications of each material.
How to Install Cotter Pins
You must install cotter pins correctly, especially when used around heavy-duty machinery or in hazardous environments, to prevent operational issues or potential health risks. To properly install a cotter pin, insert the pin into the hole of the bolt until the pin’s head is flush against the bolt. Then, using pliers, secure the cotter pin by spreading the prongs in opposing directions. Clip any excess length from the end of the pin to prevent snags or jams, but leave enough to prevent slipping through the bolt while machinery is in use.
Can You Reuse Cotter Pins?
Whether made from stainless or zinc-plated steel, cotter pins are made to last once installed. Though the materials are soft enough to bend with a pair of pliers, these pins provide a strong, reliable locking mechanism once the prongs are bent into their secured shape.
However, cotter pins are generally single-use only. Unbending and re-bending the prongs for use in another application makes them brittle and increases the risk of failure.
For the best results, if you need to replace or remove a cotter pin, discard the old pin and use a new one in its place.
How to Remove a Cotter Pin
Similar to the installation process, the removal process for a cotter pin is simple. Use a pair of pliers to straighten the ends of the prongs, then slide the pin out of the hole in the bolt. Discard the used pin and replace it with a new one to restore the assembly.
Quality Cotter Pins fr Sale at FMW Fasteners
When you work with machines or similar equipment, you often need cotter pins for securing bolts and other fasteners. These cotter pins often operate under high pressure and tension, which is why you need cotter pins that meet the highest standards of quality and durability. At FMW Fasteners, we offer a variety of cotter pins available in several lengths to accommodate your specific fastening needs.
We offer free shipping on qualified orders and no-hassle returns. We don't have order minimums, so you can browse our selection of zinc-plated and stainless steel cotter pins and order as many or as few as you need. If you have any questions about the type or size of pin that's right for your project, feel free to reach out to the FMW Fasteners team for assistance.