Full definition
A durometer hardness scale for measuring the indentation resistance of materials harder than 90 Shore A: hard rubber, rigid and semi-rigid plastics, hard polyurethane, and thermoplastic elastomers. Uses a sharp cone-shaped indenter (30° included angle vs the truncated cone of Shore A), providing higher sensitivity in the hard-material range. Per ASTM D2240 and ISO 868. Practical range: 20-80 Shore D. Approximate conversion: 90 Shore A ≈ 40-45 Shore D (overlap zone where both scales can be used). Measurement: same technique as Shore A — press durometer firmly on specimen surface (min 6 mm thick), read at 1 second. Common values: nylon 75-80D, UHMWPE 60-65D, hard PU wheels 55-75D, rigid PVC 70-85D, solid hard rubber 60-80D. Shore D is used alongside Shore A to provide a complete hardness characterization spanning from very soft elastomers through rigid engineering plastics. Per ASTM D2240 Type D. Testing at 23 ± 2°C. Also used to assess cure state of thick rubber moldings at the surface.