Posted to News on 28th Sep 2026, 11:00
A guide to external snap rings
External constant section retaining rings, commonly known as external snap rings, are designed to secure components on a shaft within mechanical assemblies. Installed into a machined shaft groove, the portion of the ring protruding from the groove creates a shoulder that retains components in place. Rotor Clip manufactures constant section snap rings in both external and internal configurations, with this guide focusing specifically on external snap ring designs.
If you work with mechanical assemblies, chances are you've come across the terms snap ring and retaining ring. While retaining ring is a broad term covering several designs, Rotor Clip uses snap ring to describe its constant section retaining ring family. This constant section design provides three points of contact with the groove while maintaining a lug-free profile also makes them well suited for applications with limited radial clearance.
In this guide, we'll take a closer look at how external constant section retaining rings work, their key design features, common applications, and the factors to consider when selecting the right ring for your application.
Internal vs external snap rings: what's the difference?
External snap rings are installed into a groove on a shaft, while internal snap rings are installed into a groove inside a housing or bore. Both are part of the constant section retaining ring family, but their installation location determines whether the ring provides retention on a shaft or within a housing.
External Snap Rings: Installed into a groove machined onto the outside diameter of a shaft. Once seated, the portion of the ring extending beyond the groove creates a shoulder that retains the assembly on the shaft.
Internal Snap Rings: Installed into a groove machined inside a housing or bore. Once seated, the protruding portion of the ring creates a shoulder that retains the assembly within the housing.
Rotor Clip's external snap ring series
Rotor Clip manufactures a complete line of external snap rings within the constant section retaining ring family. Available in both inch and metric sizes, standard external snap rings range from 0.157 to 10 (4 mm to 150 mm), with custom sizes available up to 44 (1200 mm) and beyond. Each series is designed for specific groove requirements, bearing applications, and installation needs.
External inch snap rings
USC: Once installed in the groove of a shaft, the portion of the ring protruding from the groove acts as a shoulder to hold an assembly in place and maintain external axial retention.
USH: External notched snap ring designed for installation into a groove on a shaft. Notches provide easier installation and removal.
External metric snap rings
SR: Designed for grooves in the outer tracks of ball or roller bearings on shafts.
SB: Designed to retain SAE standard metric bearings on a shaft.
CFS: External metric flat wire snap ring installed into a groove on a shaft. Meets DIN 9927.
CBS: External metric snap ring designed to retain metric bearings on a shaft. Meets DIN 5417.
CRS: External metric round wire snap ring installed into the groove of a shaft. Meets DIN 7993 Type A.
How to select an external snap ring
Selecting the right external snap ring depends on the requirements of the application, including shaft dimensions, groove dimensions, load requirements, available clearance, and operating environment. Material, finish, ring section and end configuration should be evaluated to ensure proper fit and retention within the assembly.
External snap rings are used across a wide range of mechanical assemblies where components need to be retained on a shaft. Common applications include hydraulic cylinders, steering gear assemblies, brake systems, clutch assemblies, and clevis joints. Their compact design makes them suitable for applications where space limitations and load requirements must be considered.
Custom external snap rings and constant section retaining rings
Have a unique application with specific requirements? Rotor Clip designs custom external snap rings to meet application needs that go beyond standard sizes and configurations. Our engineering team works with customers to modify constant section rings for specific design requirements. Rotor Clip's coiled-wire production process can allow nonstandard modifications to be made without special tooling, helping reduce additional costs.
Modifications include: load and rotational capacity; tolerance; section thickness; end configurations; materials and finishes; and quality and inspection requirements.
