Durometer

Durometer is the hardness value and the test instrument used to measure the indentation hardness of rubbers, elastomers, soft plastics, and other nonmetallic materials. The reading is taken from how deeply a standardized indenter penetrates under a defined load, typically on Shore scales such as A and D. It provides a 0–100 scale reading that is only meaningful within the same scale.

In manufacturing, durometer verifies material firmness for seals, gaskets, vibration isolators, urethane pads, rollers, grips, and soft tooling interfaces. On the shop floor, it predicts sealing, compression, rebound, vibration damping, wear resistance, and fit under preload. In CNC machining, durometer is critical for O-rings and seals for coolant, air, hydraulic, or vacuum systems; pucks and bumpers for fixturing; rollers for conveyors; edge-banding; and soft jaws that grip without marring. The test requires placing the part on a stable surface, pressing the durometer perpendicularly, applying standard force, and reading after dwell time. The result reflects indentation resistance, not tensile strength. For CNC cells, durometer ensures soft components behave predictably under clamping and repeated contact. For millwork and assembly, it helps select compliant components that absorb variation without telegraphing defects or crushing edges. For tolerance-driven builds, durometer controls deflection under assembly force, affecting stack-up, retention, and sealing behavior.