With hundreds of different fastener types available, it can be hard to choose which is appropriate for a given application. Although bolts and screws are the most common and have a broad utility, there are numerous specialty devices that are beneficial to be aware of. One such component is the spring pin which is a cylindrical mechanical fastener capable of compression and expansion as required. In this blog, we will discuss the fundamentals of spring pins, alongside their functionality across various applications.
Spring pins apply an outward compressive force when threaded through a hole. When no mechanical force is applied to the spring mechanism, the fastener's diameter should always be greater than the associated slot, allowing the device to stay in place. With quick and easy installation, spring pins are an efficient means to achieve a secure interface. The two most common variants, coiled and slotted pins, vary only in their body design and compression angle. Coiled pins employ a spiral shaft and provide excellent fatigue resistance across various operating parameters. Conversely, slotted pins feature a "C" shape which allows for quick assembly.
Spring pins are commonly found in automotive and industrial applications, given their stability and vibration resistance. Their design also avoids damaging the target surfaces, making these pins a preeminent choice for bearing and bushing retention. With variability in coil strength, users can choose a heavy or light-duty model based on the application material. Moreover, up to two spring pins may be applied to a hole to meet excess sheer requirements.
When choosing any fastening device, the material and coating are both salient considerations. Carbon-steel-based pins, such as the 1070 and 1095 series, offer enhanced durability and increased operational lifespan. However, these materials also require additional coating in order to prevent corrosion. Meanwhile, 300 series stainless steel is a great choice for aerospace and nautical applications where exposure to corrosive elements is more likely. In more demanding applications with less risk of corrosion, customers may opt for a 400-series stainless steel fastener.
Regardless of the base material, users should also consider the various finishes available, those of which include oil, phosphate, zinc, and cadmium. Lightly-oiled finishes are generally considered a temporizing measure to prevent oxidation during transport, but the pin should be re-oiled before installation to prevent rust. Alternatively, phosphate coatings are considered for low-corrosive environments in conjunction with a 400-series or carbon-based steel. Zinc is another cost-effective alternative featuring a larger range of operating temperatures, and it too should not be installed in most marine or aeronautical applications. Cadmium is a malleable element that is much more stable than other transition metals, making it suitable for highly-corrosive environments.
Despite their flexibility across a range of applications, there are some limitations that must be considered. Namely, spring pins are only compatible when correctly sized, meaning the target hole has a smaller diameter than the fastener. Another factor to keep in mind is that spring pins are not as precise as some bolts and screws, so it is important to assess the application's needs before choosing any particular product.
When your applications call for spring pin components you can steadily depend upon, look no further than NSN Unlimited to secure your operational requirements. As a leading aerospace parts distributor, we offer customers immediate access to a diverse inventory of over 2 billion ready-to-purchase components for a variety of niche and commercial applications. We are an AS9120B, ISO 9001:2015, and FAA AC 00-56B accredited enterprise with a No-China Sourcing policy, and our team would be happy to answer any questions you may have. To get started on the purchasing process, simply complete an Instant RFQ form for any item you are interested in, and you will receive a customized quotation within 15 minutes or less.
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