Standard sizes of Orings

An Oring is a solid-rubber seal shaped like a doughnut or torus. When compressed between mating surfaces, an Oring blocks the passage of liquids or gases. Darcoid Orings are available in a wide range of standard and non-standard sizes that are suitable for nearly all sealing applications. Two dimensions describe the size of an Oring: its inside diameter (ID) and its cross-sectional diameter (CS). Orings first became popular during World War II. One of the early standards, AN6227, contained only 88 sizes. As the usefulness and flexibility of the Oring became apparent, additional standards were developed to expand the sizes available to the engineers of the day. Today, AS-568, containing 379 sizes, is considered to be the Oring industry's standard. At Darcoid Nor-Cal Seals, you will find 26 sizes added to the 400 series alone.

There are 369 standard sizes of Orings with inside diameters ranging from 0.029 to 25.940 inches and cross sections ranging from 0.040 to 0.275 inch. Standard sizes are available in five popular cross-sectional diameters (0.070, 0.103, 0.139, 0.210 and 0.275 inch). Each Oring size is identified by a "dash number." Each Darcoid Nor-Cal Seals' "dash number" is the same as Aerospace Standard AS568B, Aerospace Size Standard for Orings. Those designations are used throughout the Oring industry.In addition, Darcoid Nor-Cal Seals also offers all 20 sizes of boss seals used for sealing straight-thread tube fittings on a boss. When pressed between two mating surfaces, Orings block the passage of liquids or gases. Orings can form a static or dynamic seals.

Orings

A static seal is where the Oring does not move and is used simply for containing pressure or maintaining a vacuum. Dynamic seals can be reciprocating (like a piston and cylinder), or rotating (shaft rotating in a housing). Axial squeeze and radial squeeze are two methods for applying an Oring. An axial squeeze is when the ring is compressed parallel to a line drawn through the center or axis of the ring. In a radial squeeze the ring is compressed between the internal diameter (ID) and overall diameter (OD). Also, a boss seal is an Oring, however it just doesn't fit the standard sizes for an Oring. A boss is a cylindrical projection on a casting or forging. The end of that projection is machined to provide a flat, smooth surface for sealing. Straight threads used with Orings provide a better seal than tapered threads used alone. Darcoid Nor-Cal Seals offers Orings in all 369 standard sizes and has hundreds of molds for non-standard sizes.