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Centrifugal Capacity Retaining Snap Rings

ANSI Hardware Design Data

Centrifugal Capacity Retaining Snap Rings

Proper functioning of a retaining snap ring depends on the ring remaining seated on the groove bottom. External rings “cling” to the groove bottom because the ring ID is slightly smaller than the diameter at the bottom of the groove. Ring speed should be kept below the allowable steady-state speed of the ring, or self-locking rings specially designed for high-speed applications should be used, otherwise an external ring can lose its grip on the groove. Applications of large retaining rings that tend to spin in their grooves when subjected to sudden acceleration or deceleration of the retained part can benefit from a ring with more “cling” (i.e., a smaller interior diameter) as long as the stress of installation is within permissible limits. Special rings are also available that lock into a hole in the bottom of the groove, thereby preventing rotation. 

The following equation can be used to determine the allowable steady-state speed N of an external spiral retaining ring:

Snap Ring Centrifugal Force

Open: Centrifugal Capacity Retaining Snap Rings Calculator


N = Speed in revolutions per minute, 
C1 = Minimum ring cling to groove bottom, 
E = Ring radial wall,
Rn = Free neutral ring radius,
Ro = Free outside ring radius,
Ri = Free inside ring radius, all in inches. 

For external spiral rings, the minimum ring cling is given by: C1 = (C − G)/G


C = Mean groove diameter in inches
G = Maximum ring free ID in inches.

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