What are spring pins?
Spring pins, also known as slotted pins, rolled pins, or tension pins, are cylindrical fasteners with chamfered ends that are used to secure two or more parts together. They are made from alloy steel, carbon steel, or stainless steel, and have a spring-like elastic property. Spring pins are wider than the hole they are inserted into, but deform and expand to achieve the same diameter as the hole.
Spring pins are used as locking devices, positioning points, anti-chafing surfaces, shafts, or sleeves for wiring. For example, in airplanes, spring pins are used to hold multiple parts together in a position where the parts are relative to each other.
Spring pins come in two types
Slotted pins
In a slotted pin, the sheet material is curved around by less than 360 degrees, leaving a gap into which the pin can compress. These types of pins are typically used in lighter-duty applications or where rigidity is required.
Spiral pins
A spiral pin is typically made from a lighter gauge of sheet material than a slotted pin, but it's curved around by more than two complete revolutions. This results in a strong pin that retains flexibility. This can reduce stress concentrations and fatigue failures.
Spring pins provide extra security in parts of assemblies prone to jolts or vibration. The pin is sprung so that it can decrease in diameter when installed, allowing for a snug fit while exerting a retaining force against the walls of the hole.
When compressed into a hole, the pin exerts a force against the sides of it, as it attempts to expand to its resting diameter. This force results in friction, which retains the pin securely in the hole.
