PROEXPORT / TECHNICAL KNOWLEDGE
How to Specify Roller Covering Hardness: Shore A, Shore D, Vickers HV
Durometer hardness is a contact elasticity index, not a complete structural specification. Review measurement standards ISO 7619-1, ISO 868, ISO 6507-1, and wall-thickness influence on readings.
KNOWLEDGE & PRACTICE
Hardness Measurement Scales for Industrial Rollers
| Hardness Scale / Standard | Indenter Geometry | Typical Material Range | Critical Measurement Constraints |
|---|---|---|---|
| Shore A (ISO 7619-1 / DIN 53505) | Truncated cone (Ø 0.79 mm, 35° angle) | Soft elastomers, rubber, polyurethane (20–95 ShA) | Layer thickness must be >= 6 mm; thin layers reflect core stiffness |
| Shore D (ISO 7619-1 / ISO 868) | Sharp point cone (R 0.1 mm, 30° angle) | Rigid polyurethane, ebonite, technical plastics (40–85 ShD) | Used when Shore A exceeds 95; tests rigid plastic coatings |
| Vickers HV (ISO 6507-1) | Diamond pyramid (136° face angle) | Hard chrome plating, plasma ceramics (800–1800 HV) | Load typically 0.1–1.0 kgf (HV0.1–HV1); prevents punching thin chrome |
| Rockwell HRC (ISO 6508-1) | Diamond cone (120° angle, 150 kgf) | Hardened steel roller base shafts (45–62 HRC) | NEVER use directly on chrome coatings < 100 µm (cracks the layer) |
KNOWLEDGE & PRACTICE
The Thin-Layer Effect: Why 2 mm Coverings Mislead Shore Durometers
ISO 7619-1 specifies that reliable Shore hardness measurements require a minimum specimen thickness of 6.0 mm. In industrial practice, roller coverings often measure between 2.0 mm and 4.0 mm in radial wall thickness.
When a durometer indenter presses into a thin 2 mm rubber sleeve, the rigid steel core immediately absorbs the penetration force. A true 60 Shore A compound will register as 72–75 Shore A on the durometer dial. At PROEXPORT, we employ micro-hardness testers (IRHD Micro according to ISO 48-2) or measure calibrated 6 mm test pucks produced from the identical vulcanization batch.
KNOWLEDGE & PRACTICE
Why Hardness Alone Fails to Predict Contact Behavior in Nips
- Two coverings with the exact same 70 Shore A reading can exhibit completely different compression moduli (Young’s modulus E), generating vastly different nip contact widths under the same linear force.
- Rubber hardness drops by 3 to 8 Shore points as temperature rises from 20°C to 80°C. Machine calibration must account for hot-running equilibrium.
- Hardness does not measure traction: a 60 ShA polyurethane roller has a different coefficient of friction compared to a 60 ShA silicone roller.
PROEXPORT / INDUSTRIAL ROLLERS
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