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Calculating Thrust Load Capacity for Retaining Rings

Retaining Ring Assembly

Load Capacity of Retaining Rings and Grooves

Rings usually have two load statistics, thrust load capacity based on ring shear and thrust load capacity based on groove yield. The lower of these two theoretical values is the thrust load capacity of the system, because once the lower value is reached, the system will fail. In most cases, the thrust capacity of the groove is the determining (lower) value. In thrust load calculations, a safety factor is used to account for imperfections in the system. Typically a safety factor between 2 and 4 is used for calculations of thrust load capacities.

Thrust Load Capacity based on Ring Shear is the load capacity of the ring. This is the theoretical amount of load that the ring can withstand before it shears (gets cut). The theoretical value is based on the overall thickness of the ring and the shear strength of the ring material.

Thrust Load Capacity based on Groove Yield is the load capacity of the groove. This is the theoretical amount of load that the groove can withstand before it deforms and fails. The theoretical value is based on the depth of the groove and the yield strength of the groove material.

How to calculate capacity based on Ring Shear

To calculate the theoretical thrust capacity of a retaining ring's shear strength, the equation to the left is used.

The variables are:

B: The diameter of the bore or shaft.
t: The overall thickness of the retaining ring.
Ss: The shear strength of the retaining ring material.
pi: 3.14
K: Factor of safety. Typically 3 or 4.

How to calculate capacity based on Groove Yield

To calculate the theoretical thrust capacity of a groove, the equation to the left is used.

The variables are:

B: The diameter of the bore or shaft.
d: The depth of the groove.
Ys: The yield strength of the groove material.
pi: 3.14
K: Factor of safety. Typically 2 or 3.

Effects of Groove Materials

In situations where the an assembly is held together by a retaining ring, the strength of the groove frequently determines the load capacity of the system. Using different groove materials can alter thrust load capacity of the groove. See the table below to find the yield strength of common materials used for bores or shafts.

Material Yield Strength(psi)
Hardened Steel 145,000
Mild Steel 45,000
Cast Iron 32,000
Brass (Cold Rolled) 60,000
Brass (Soft) 18,500
Zinc Alloy 21,500
Aluminium 18,000

Effects of Ring Materials

Similarly to groove strength being tied to groove material, a ring's material has an impact on its shear strength. Many different types of raw material forms are used in the manufacturing process of rings (rolls, wire, soft steel), and each form can have varying shear strength values based on the overall thickness of the material. For questions regarding shear strength capacity of a non-standard material, please contact us.
Solon, OH
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