|The Introduction Of Retaining Rings(Circlips)
What are retaining rings?
Retaining rings are are precision engineered components that holds components or assemblies on shafts or in housings/bores when installed in a groove. Once installed, the exposed portion acts as a shoulder which retains the specific component or assembly. Self-locking 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 corrosion protection depending on the type of environment in which they are used.
How are retaining rings used?
Retaining Rings work by creating a shoulder that can hold components in place. The retaining shoulder is created when the ring attaches itself to the bore or shaft, typically by snapping into a groove. Ordinarily (however not always) a groove is dug into the shaft or bore, and this groove becomes the seat for the retaining ring. Retaining rings are designed such that their contact diameter has some interference fit with the groove in which they fit. This creates a "snug" fit between the ring and groove. The term used to describe the amount of interference fit is "cling".
Cling causes the retaining ring to fit tightly and securely against its groove bottom. Without cling a ring would have a loose fit and would "rattle" in its groove. This lack of cling would decrease the retention capacity of the ring because a "cling-less" ring is free to move radially, creating weak retention points that will ultimately cause the assembly to fail. Another key factor is the width of the groove. The groove width is slightly larger than the rings thickness, thus creating a snug axial fit. The tight axial fit along with the cling to the groove bottom create a rigid shoulder which can retain thrust loads.
What advantages does a retaining ring have when compared to a permanent shoulder?
Instead of using a retaining ring, it is possible to machine a permanent shoulder on to a bore or shaft. Creating a permanent shoulder requires one to start with a larger than desired shaft (or a thicker than desired bore), and to machine away material to create the desired size. While removing the material, we would leave untouched the area where we want the shoulder to be. This approach has two disadvantages. First, the initial material will be bigger and therefore more costly. Second, the machining will take time, further adding to the cost.
To use a retaining ring in the same situation, we need only buy a shaft with the desired shaft size, and then machine away a groove for the ring. We then install the ring to create the shoulder. We start with a less expensive piece of material because it is smaller, and machine away only the groove, which is much quicker than machining away large areas of the shaft.
There are some instances where a permanent shoulder is the only solution. One variable to look at is the amount of load that the shoulder will be required to hold. If a retaining ring cannot be found that has a sufficiently high thrust load capacity, a permanent shoulder may be required.
What advantages do retaining rings have over traditional fasteners?
Holding assemblies together using traditional fasteners such as bolts, cotter pins and end caps requires more machining and forethought than assemblies that are secured using retaining rings. The reason is that traditional fasteners often require threaded components, mating threaded holes, counter-bores, and access holes. Retaining rings require only a groove, and in some cases not even a groove is required.
What are some other names for retaining rings?
constant section rings
tapered section rings
round wire rings
square section rings
push-on fix/grip rings
What are some places that retaining rings are used?
piston wrist pins
How to select a retaining ring.
The following design parameters should be considered When selecting a retaining ring:
Internal or External