The AS568 O-Ring Size Standard and Why It Saves You Tooling

What AS568 Actually Is

AS568 is the aerospace derived standard that fixes a family of O-ring inside diameters and cross sections, each identified by a dash number. Its usefulness is not technical elegance. It is that a tool already exists somewhere in the world for every size in it, so a designer who stays inside the standard never pays for a mould.

Why We Hold the Complete Mould Set

We possess all the moulds for the AS568 O-ring size range, which is why we can supply standard parts from the series promptly. For a buyer this means a standard dash number is a stock production item rather than a tooling project, and the compound becomes the only open question.

AS568 O-Ring Series →

Reading a Dash Number

A dash number encodes a cross section family and a size within it. The practical consequence is that two parts with similar inside diameters may have very different cross sections, and a cross section mismatch is the most common cause of a seal that fits the groove diameter and still leaks. Always quote the full dash number rather than measuring the inside diameter alone.

When to Stay Standard and When Not To

If your groove is not yet fixed, design it around a standard dash number and you remove a tooling cost and a lead time from the project permanently. If the hardware is already in production, then the size is what it is, and the right answer is a properly tooled non standard seal rather than the nearest standard size forced into the groove. Our mould workshop cuts those tools.

Where AS568 O-Rings End Up

The range of equipment using these sizes is very wide: machine tools, agricultural machinery, instrumentation, construction machinery, automobiles, ships, aerospace equipment, engineering machinery, chemical machinery, mining machinery, plastic machinery and petroleum machinery. That breadth is exactly why standardising on the series is worth doing.

O-Rings →