Retaining Rings FAQs

A retaining ring (often referred to as a circlip or snap ring) is a fastener that holds components or assemblies onto a shaft or in a housing/bore when installed. Circular push-on retaining rings may be installed in applications where there is no groove. Retaining rings are typically made from carbon steel, stainless steel or beryllium copper and may feature a variety of finishes for aesthetics and corrosion protection depending on the type of environment in which they are used.

Retaining rings can do the same job for a lot less. A simple groove is all that’s needed to accommodate a retaining ring. Other fastener methods, like nuts, require machining threads, which is more costly, and wastes additional materials. Retaining rings will not require periodic re-torquing as a nut and bolt might. Retaining rings are easier to install than fasteners with multiple components, either manually or in automated assembly equipment, reducing labor costs.

Rotor Clip manufactures sizes of retaining rings that are capable of withstanding thrust loads well in excess of 260,000 lbs (roughly 118,000 kg). Our retaining rings are used in everything from safety-critical automobile transmission and braking equipment to home and spa appliances, earthmovers and miniature medical devices. Rotor Clip retaining rings exceed the holding power required per specifications for any application.

Retaining rings are installed using a number of different methods depending on the application and ring series. We support our retaining rings with a complete line of manual and pneumatic tools. Our engineering design team can assist you in designing custom application equipment for specialized or high volume assembly.

Selecting a standard retaining ring will always be more cost effective than designing a custom retaining ring. A standard retaining ring will save on engineering time, eliminate potential production issues and ensure timely delivery of product. A Rotor Clip technical sales engineer will be able to recommend a suitable standard production alternative to a custom retaining ring. Should a custom ring be required for a specific application, our engineering design team will review the blueprint supplied by our customer and advise feasibility of production, price and delivery. As Rotor Clip is entirely vertically integrated, we have a tool and machine shop located on-site to develop, produce and repair all of our own tools in-house.

An inverted retaining ring would be used when specifications require that another assembly must pass through the housing of your application. Review the Clearance Diameters “L1” and “L2” dimensions on the Product Part Pages online or in the Rotor Clip catalog. This will tell you if the lugs of the ring will interfere with this assembly. If this is the case, you can select an HOI (HOusing Inverted) or SHI (SHaft Inverted) for a shaft application. These rings feature inverted lugs for better clearance.

If your application can accept either an axial or a radial retaining ring, shoulder size, thrust load and RPM can determine which type you use. Be sure to check these specifications carefully before making your selection. Take into consideration that radial rings offer enlarged shoulder dimensions for part retention and generally cost less than standard axial rings.

If you select an E ring and later discover that it cannot withstand the RPM generated by your application, you can select a standard, heavy duty RE (REinforced) ring, which will withstand higher RPMs and can accommodate higher thrust loads. RE rings fit into the same grooves as E rings and can be easily interchanged without redesigning the application.

The E ring specification pages in the Rotor Clip catalog list many variations. For example, E-18, SE-18, YE-18 and ZE-18 are not specials but simply different parts that can be used on the same shaft size. They will function in applications having either different groove diameters/groove depths for the same size shaft (3/16″). They also offer optional geometry for a specific shaft size. Often, the Outer Dimensions (O.D.), ring thickness and groove dimensions vary for SE, YE and ZE part numbers.

The POL (light) rings are thinner than the standard PO rings. The PO and POL series rings are available with different specifications in the same size, similar to the variations available in the E and RE series. POL rings differ in groove width requirements, ring thickness and maximum and thrust load requirements.

SHR rings may be used when increased thrust loads and RPM limits are required. An SHR (Reinforced) ring is a heavy-duty version of an SH ring with increased thickness and minimum/maximum sections. Keep in mind that an SHR requires a wider groove than an SH when determining which ring will better suit your application.

Some retaining rings are listed twice in the catalog. For example, HO-156. This indicates that the same ring will function in two separate applications that have different housing/shaft and groove sizes. Online, these parts will be noted with an Optional Bore or Shaft designation on the part listing.

Free Diameter, Axial Rings: This dimension can only be measured accurately on rings that have never been installed. Measuring free diameter on an HO ring where the lugs have been compressed (or on an SH ring where they have been expanded) will yield a false reading.

Free Diameter, Axial Inverted Rings: The standard way of measuring free diameter for an axial ring does not hold true for an HOI and SHI retaining ring, as the lugs interact with the free diameter measurement. For the correct method, see the HOI and SHI specification pages in the Rotor Clip catalog.

Free Diameter, Radial Rings (ie: E/C/RE/DE/DC series rings): Do not take this measurement on an E ring using a caliper. The correct way is to use a pin gauge that makes three-point contact with the ring’s prongs.

Hardness: To check hardness effectively, you must first remove any finishes from both sides of the ring. Using a properly calibrated hardness tester, take a reading on the ring with the burr side up. Compare results to those listed in the hardness tables of the catalog specification page for that ring.

An external axial ring (SH, SHI, etc.) can be over-expanded during installation. To prevent this, take a pin gauge 1% larger than the nominal shaft diameter of your application. Using Rotor Clip retaining ring pliers and safety goggles, expand the ring and release it on the gauge. With the tips of the pliers still in the lugs, adjust the stop on the pliers to this opened setting.