How to Specify Standard O-Rings:
O-Rings are specified by calling out (a) the O-Ring size,
and (b) the compound (or compound number). Also included normally is the hardness measured
in "durometer." O-Rings are typically 70 durometer with 80 and 90 being harder compounds and
60, 50, and 40 being softer. Durometer is typically part of the compound designation.
How to Select a Standard Size:
O-Rings are available in 349 standard sizes as set up by the Aerospace Standard 568 (AS568)
published by the Aerospace Division of the Society of Automotive Engineers. These sizes are
designated by "dash" numbers as shown on the SIZE CHART .
An O-Ring with an inside diameter (I.D.) of .362 ± .007" and a cross section (W) of .103 ± .003" is designated as: AS568-110. It is a
common practice in the O-Ring industry to drop the "AS568" prefix and refer to this O-Ring as a
-110 (pronounced: dash one ten) or simply as a 110 (one ten).
When designing an O-Ring for a given application, it is desirable to try to use a standard
size to insure low cost and ease of supply. Keep in mind that there may be a tooling charge for
non-standard sizes.
Note: For O-Rings that do not fall in the standard sizes, determine the actual inside
diameter (I.D.) and the cross section (W) and we can quote according to that information. Also
refer to our section under METRIC
O-RINGS for information on the availability of O-Rings that might fit your requirement.
Select a Compound
Compounds are available in a variety of elastomers such as Nitrile, Neoprene, Ethylene
Propylene, Fluoroelastomer, etc. To select the proper elastomer, check:
- Compatibility with the fluid media to be sealed, from the
FLUID MEDIA GUIDE.
- General properties required, from the
PROPERTIES CHART.
Once the base rubber compound and the durometer are known, we can assist you to select a
specific compound. If the rubber chosen is Neoprene (Chloroprene) and the durometer required
is 70, compound C70, our standard Neoprene, might be a perfect choice.
Call us at 817-861-8144 for compound assistance. There are hundreds of compounds available to satisfy the requirements of your application.
The final O-Ring part number for the size and compound listed above is as follows: AS568-110 C70. For simplicity sake, we refer to this O-Ring as a 110C70.
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