Author: Site Editor Publish Time: 2026-10-21 Origin: Site
When you specify a rubber or silicone part, one number drives almost everything downstream: Shore A hardness. It tells a buyer, engineer, and molder how stiff the part will feel, how much it will compress, and how it will behave under pressure and temperature. This guide explains what Shore A measures, the ranges used for common seals, and how to choose the right durometer for O-rings, gaskets, and custom molded parts.
Shore A is a durometer scale for flexible rubbers and elastomers. A calibrated gauge presses a spring-loaded indentor into the material; the depth of penetration is converted to a reading from 0 (very soft) to 100 (rigid). Softer gels and foams use the Shore 00 scale; plastics use Shore D. For molded rubber components, the useful window is roughly 30–95 Shore A, with most industrial seals falling between 40 and 90.
Hardness is a trade-off, not a “higher is better” spec:
The table below shows common durometer choices for standard rubber components. When an O-ring must also match a dimensional standard, pair the hardness with the correct size from the AS568 O-ring size chart.
| Component | Common Shore A | Why |
|---|---|---|
| General-purpose O-rings | 70 | Balanced squeeze, compression set, and extrusion resistance |
| Low-temp / high-compression O-rings | 60–65 | Better cold flexibility and conformance |
| High-pressure static seals | 75–90 | Resists extrusion into the gap |
| Flat gaskets | 50–70 | Conforms to flange imperfections |
| Diaphragms | 40–70 | Flexibility and low stress relaxation |
| Vibration mounts / bumpers | 45–75 | Damping without bottoming out |
Hardness is measured per ASTM D2240 / ISO 7619. The durometer is placed on a flat specimen of adequate thickness (typically ≥6 mm) and the reading is taken after the indentor has rested for about 15 seconds under a fixed load. Readings on curved, thin, or uneven surfaces are not valid, so molded test buttons or finished-part flats are used for verification.
Start from the service condition, not a habit:
Anlintech molds rubber and silicone parts across the full Shore A range in FKM, silicone, EPDM, NBR, HNBR, and FFKM. We verify durometer on every production lot and can hit tight tolerances per ISO 3302-1 for your drawing. Send the target hardness, service environment, and geometry for a quote; we provide material certification and hardness test reports with shipment.
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