Asker Durometer Testers

Q: Why does ASTM D2240 recommend omitting Durometer readings below 20 or above 90?

Per ASTM D2240 Section 9.3 , indentation readings below 20 or above 90 on any given Shore scale lose linearity at the extreme ends of spring travel. If your material tests above 90 on a Shore A Durometer, switch up to a Shore B or Shore D scale; if it reads below 20 on a Shore A Durometer, step down to a softer scale such as Shore O , Asker C , or Shore OO .

F.A.Q.

Why does ASTM D2240 recommend omitting Durometer readings below 20 or above 90?

Per ASTM D2240 Section 9.3, indentation readings below 20 or above 90 on any given Shore scale lose linearity at the extreme ends of spring travel. If your material tests above 90 on a Shore A Durometer, switch up to a Shore B or Shore D scale; if it reads below 20 on a Shore A Durometer, step down to a softer scale such as Shore O, Asker C, or Shore OO.

What is the minimum sample thickness required for standard Shore A and Shore D testing?

Standard Shore A and Shore D indenters require a minimum specimen thickness of 6 mm (0.24") so the hard surface of the test table does not influence the reading ("anvil effect"). While thinner layers can be stacked (up to 3 plies) if the surfaces are completely flat, the most accurate solution for specimens as thin as 0.050" (1.25 mm) or small O-rings is a Type M Durometer (Rex 1600-M or Rex DD-4-M) mounted in the Rex OS-3 Type M Test Stand.

What is the difference between a standard dial Durometer and a Max-Hand (Memory Pointer) model?

A standard dial gauge like the Rex 1600 has a single active pointer that shows live hardness as long as the presser foot is held against the specimen. The Rex 2000 Max-Hand Shore Durometer (which replaced the RX-1700) adds a second peak-hold pointer that locks at the maximum initial reading while the active pointer creeps downward, allowing the operator to record both peak hardness and material relaxation (creep) simultaneously.

What is the difference between a Durometer Test Block and a Durometer Verifier?

Color-coded rubber test blocks (included with most Durometers) allow operators to perform a quick daily functional check to confirm the indenter and spring "feel" are operating properly, but they should not be used to recalibrate a gauge. To formally verify and certify the spring load accuracy of Shore A and Shore D probes across 10 to 90 Durometer units in-house, use the electronic load-cell-based DeFelsko SHDVERIFY PosiTector SHD Verifier Kit.

Asker X Series High Performance Durometer

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Asker X Series High Performance Durometer

Asker X Series High Performance Durometer
X Series measures hardness scales:
Shore A Normal rubber
Shore D Hard rubber and plastics
Asker C Soft rubber
Asker E Soft rubber
Asker F Urethane foam, sponge

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