An o-ring is an "O" shaped object usually made of an elastic material known as an elastomer. O-rings serve to create a seal between two mechanical components by preventing leakage and maintaining pressure through deforming to the shape of their surrounding cavity. This simple, cost-effective device was patented by 72 year old inventor and machinist Niels Christensen in 1937. His design proved critical to the US WWII effort, spreading rapidly throughout industry.
More about O-rings:
Due to the elastic nature of their elastomeric material (called a rubber compound), o-rings exhibit the ability to be stretched larger than originally molded under stress, but return to original size once that stress is removed. Stretching an o-ring introduces stress at its contact surfaces. Fluid (gas or liquid) remains contained so long as the pressure of the fluid doesn't exceed the contact stress of the o-ring.
O-rings are usually characterized by material (or compound), durometer (Shore A hardness) and dash number. The dash number refers to a specific inner diameter (I.D.), outer diameter (O.D.), and cross section (C.S.) based on the Society of Automotive Engineers (SAE) Aerospace Size Standard for O-rings, or simply AS568 standard sizes. Other size standards do exist, including metric (in millimeters rather than inches) and Japanese Industrial Standards (JIS)
Radial O-ring Groove Design: One popular form of the o-ring is the radial or radial gland design. Variables to keep in mind are cross section (CS) diametral squeeze, gland depth (c), groove width (w),and radius (r).
(updated 12/2008)
