Everything You Need to Know About Wrist Pin Materials, Finishes, and Coatings

The modest wrist pin is one of the most underrated components of any performance or race engine. But given how much wear this component must withstand, it’s critical to select the right pin for your application.

The reciprocating portion of any internal combustion engine focuses two massive loads on the wrist pin. Moreover, these forces work in opposite directions—compressive loads attempt to collapse the connecting rod while the high rpm generates significant torque in the reverse trend. On average, the wrist pin shuttles about 11,000 pounds of force up and down the bore, making it essential for high engine performance.

When choosing a wrist pin design for a performance engine, keep these considerations in mind:

Material

Among the hundreds of steel alloys readily available on the market, only a few are suitable for race engines. Ultimately, the tensile strength and yield strength determine how much load the steel pin can take before it fractures or becomes permanently deformed. Specialized cold rolled steel alloys are designed for wrist pins that offer high strength and durability.

When considering the material, you also need to take the thickness into account. More thickness means more strength, but it also means more weight. Your technician will be able to guide you better, depending on the application. In general, a thicker pin is better when you’re dealing with higher cylinder pressure loads or when the priority is increased endurance.

Finish

Once you’ve chosen the right material, you need to consider the finish of your wrist pin. On a microscopic level, wrist pins have valleys and peaks that retain oil and cause metal transfer between the piston and the wrist pin. Ultimately, this leads to lower engine performance.

The Super Finishing process is an optional step where the wrist pins are rolled through a machine that knocks off the peaks. This results in a much smoother finish and reduces the chances of metal transfer.

smooth-engine-parts-with-dlc-coating

Coatings

Diamond-Like Carbon (DLC) coating is an excellent addition to your wrist pin. A durable DLC coating includes a thin layer of graphite that offers incredible resistance against wear. The coating gets the name “diamond” because the hardness of the coating is similar to that of diamonds ensuring greater strength.

It has a more even surface than the base metal with enhanced lubricity and can significantly improve your engine performance levels.

If you think that DLC coatings may be right for your wrist pins, get in touch with NISU Labs. With nearly 25 years of experience in the industry, they can develop premium DLC coatings and wear-resistant solutions that suit your product needs perfectly.

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