O-Rings
An O-ring is a ring-shaped rubber seal with a circular cross-section. It is installed in a groove and compressed against the mating surface to seal fluids such as water, oil, air, and chemicals. The compressed rubber's resilience, together with the fluid pressure pushing the O-ring against one side of the groove, closes the gap. Dimensions are expressed as inner diameter and cross-section diameter (wire diameter). In Japan, standard designations include P (dynamic and static) and G (static) under JIS B 2401; in the automotive field, JASO F 404; and in the aerospace field, AS 568. They are used in hydraulic and pneumatic equipment, automobiles, and aircraft, for both moving parts such as pistons and rods and stationary parts such as flanges.
-
O-Rings
O-Ring (JASO F 404, for Reciprocating and Static Use)
O-ring compliant with JASO F 404 standard for reciprocating and static sealing applications. Available in many designation numbers by combination of inside diameter and cross-section.
JTEKT Corporation
-
O-Rings
O-Ring (AS 568 Aerospace Hydraulic)
O-ring for aerospace hydraulics compliant with AS 568, covering cross-section diameters from 1.02 mm to 6.98 mm.
JTEKT Corporation
-
O-Rings
O-Rings and Backup Rings
O-rings by material, including NBR, FKM and EPDM, that conform to standards, and PTFE backup rings. Selected according to application requirements such as oil resistance, heat resistance and chemical resistance.
JTEKT Corporation
-
O-Rings
O-Ring
O-rings used for sealing water, oil, air, various gases and chemicals. Available in a wide range of sizes and types.
JTEKT Corporation
-
O-Rings
O-Ring (Recommended Housing Dimensions for Static Applications)
Shows recommended groove dimensions and backup ring configurations for static-application O-rings with cord diameters of 1.5 to 10 mm.
SKF
-
O-Rings
O-Ring (Static Application Recommended Housing Dimensions)
Recommended housing dimensions for static-application O-rings, including combined dimensions with backup rings. Covers cross-section diameters of 1.5 to 10 mm.
SKF
-
O-Rings
R13 O-Ring
Model: R13
O-ring for open housing. Available in a variety of materials including ECOPUR.
SKF
-
O-Rings
Static Seal
A seal product group used for sealing stationary parts. It is listed in the table of contents of this document, but its body text is not included in the excerpt.
SKF
How to choose O-Rings
-
1. Specify dimensions by standard and size number
For series such as JIS B 2401 P and G, JASO F 404, and AS 568, the inner diameter, cross-section diameter, and recommended groove dimensions are defined for each size number. Confirm which standard series the equipment groove is designed to, and select a size number from the same series to avoid dimensional mismatch with the groove.
-
2. Select an inner diameter that suits the groove and shaft diameter
Select the inner diameter d1 to match the diameter of the shaft or groove bottom it fits onto. For applications sealing the outer periphery, the O-ring is generally installed with slight stretch over the shaft; for applications sealing the inner periphery, it is generally fitted along the bore side. Excessive stretch thins the cross-section and reduces squeeze.
-
3. Check the cross-section diameter against groove depth
The relationship between cross-section diameter d2 (wire diameter) and groove depth determines the squeeze. Even with the same inner diameter, some series have different cross-section diameters, so select a wire diameter that suits the groove depth and width. The cross-section diameters of the listed products range from 1.02 to 10 mm.
-
4. Select a material suited to the fluid and temperature
NBR is suitable for mineral-oil-based hydraulic fluids; FKM for heat and chemical resistance; and EPDM for water, steam, and brake fluid, but it is not suitable for mineral oils. VMQ (silicone) can be used from low to high temperatures, but its mechanical strength is lower. Confirm the fluid type and operating temperature range together.
-
5. Select hardness according to pressure
Hardness (Durometer A) is generally around 70 as standard; at higher pressures, selecting a harder material helps suppress extrusion into the gap. However, a harder material requires greater force to compress and slightly reduces sealing performance at low pressure.
-
6. Use backup rings under high pressure
In high-pressure or dynamic applications, the O-ring may extrude into the gap and be damaged. Prevent this by installing backup rings, such as those made of PTFE, on the side opposite the pressurized side. Use one for single-side pressure, or two when pressure acts from both sides, and widen the groove width to accommodate their thickness.
This guide was written by AI based on the listed products' documents and specification items. Check each manufacturer's documents before adopting.