Full definition
The standard hardness scale for measuring the resistance of vulcanized elastomers to surface indentation, using a durometer instrument per ASTM D2240 and ISO 48-4. The Shore A scale uses a truncated cone-shaped indenter pressed into the rubber surface by a calibrated spring; the depth of penetration is converted to a 0-100 reading (0 = full penetration/very soft, 100 = zero penetration/very hard). Practical rubber range: 20 Shore A (very soft gel pads, sponge cord) through 90 Shore A (very hard solid rubber, rigid PU). Common industrial hardness values: seals and gaskets 60-80A, vibration mounts 40-60A, industrial sheet 50-70A, hose tube 50-65A, conveyor belt covers 55-65A. Measurement procedure: specimen minimum 6 mm thick, flat, clean; apply durometer firmly; read at 1 second (ASTM) or 3 seconds (DIN 53505); minimum 5 readings averaged. Temperature: 23 ± 2°C standard. Tolerance: typical specification ±5 Shore A. Hardness is the most commonly specified and field-tested rubber property. Above 90 Shore A, transition to Shore D scale for hard rubber and plastics.