SAE AS568 O-Ring Gland Sizing

Dash-number gland dimensions, squeeze windows and extrusion-gap limits for SAE AS568 O-rings from 0.070 in through 0.275 in cross-section.

AS568 dash-number gland dimensions

SAE AS568 O-Ring Gland Sizing calculations for as568 dash-number gland dimensions are computed deterministically from published formulas, so the same inputs always produce the same result and the same OAS-XXXX verification hash.

Squeeze windows by cross-section series

SAE AS568 O-Ring Gland Sizing calculations for squeeze windows by cross-section series are computed deterministically from published formulas, so the same inputs always produce the same result and the same OAS-XXXX verification hash.

Extrusion gap and backup ring sizing

SAE AS568 O-Ring Gland Sizing calculations for extrusion gap and backup ring sizing are computed deterministically from published formulas, so the same inputs always produce the same result and the same OAS-XXXX verification hash.

Engineering summary

Governing parameters for the SAE AS568 O-Ring Gland Sizing silo.

Governing parameters and computed results for this calculation
Parameter Value
Cross-section range 0.070–0.275 in
Dash series 0xx · 1xx · 2xx · 3xx · 4xx · 9xx
Static squeeze target 15–25 %
Dynamic squeeze target 10–18 %
Governing standard SAE AS568

Frequently asked questions

What squeeze percentage should a static AS568 gland use?
Static face and radial seals target 15% to 25% squeeze. Below 15% the seal may not seat against surface finish and pressure; above 25% compression set accelerates and the elastomer takes a permanent set.
How is the AS568 dash number related to cross-section?
The dash series fixes the cross-section: 0xx is 0.070 in, 1xx is 0.093 to 0.103 in, 2xx is 0.139 in, 3xx is 0.210 in and 4xx is 0.275 in. The 9xx series are SAE Boss ORB sizes at 0.087 in.
When does an O-ring gland need a backup ring?
Add a backup ring when the extrusion gap exceeds the elastomer's allowable gap at the operating pressure and temperature. The backup ring groove width grows with each ring: the 0-ring, 1-ring and 2-ring widths are tabulated per dash size.