Durometer Testing

The durometer is the international standard for the hardness measurement of rubber, plastic, and other non-metallic materials. Durometers are described in ASTM Std. D2240. Type A is used for soft rubber, plastics, elastomers, and printers’ rolls; type D is for hard rubber, thermoplastics, floor coverings, and similar materials.

Durometers determine hardness by measuring the penetration of an indentor into a specimen. With the Model 1600 or 1700, this can amount to as much as .100", (0.25cm); be sure your specimen is thick enough to preclude any chance of the anvil sensing the hardness of an underlying surface. Low durometer materials should be at least .250" (0.63cm) in thickness; thinner high durometer sample pieces can be tested accurately because the anvil penetrates less deeply. For materials as thin as .050" (0.13cm), the Rex Type M Micro-A Durometer is recommended.

The durometer hardness test can be used to indirectly measure other material properties, such as tensile modulus, resilience, plasticity, compression resistance, and elasticity – a set of material specimens is first tested on a standard tester for the property of interest, following which durometer readings are recorded on the same samples. The correlation for many properties is close enough to allow monitoring by only durometer testing thereafter.

Rex Dial Durometers

The Model 1600 is Rex’s best-seller for good reason – it produces readability to within 1/2 point – the best accuracy for maximum measurements at a minimum cost. Large 2.25" dial with full 360° sweep. The Model 1700 enables the user to observe and measure creep (the tendency of the indentor to continue penetrating a specimen over time). It records maximum and current readings, allowing quantification of creep.

Both models are supplied with a custom made carrying case. Full one year warranty. The Model 1600A is generally in stock; other types A and D are readily available; types B, C, DO, O, OO, and OOO are available by special order. Please call for literature, prices, and details. Operating stands and other accessories are also available.

Rex Digital Durometers

The Rex DD-3 Digital Durometer is an excellent instrument for critical data collection or repetitive quality control testing. Features of this durable, accurate unit include a large direct drive LCD display, RS232 data ports for computer compatibility, tolerancing, a locking feature to prevent accidental erasure of tolerances, automatic shutoff, low battery warning, and 0.1 resolution. MTI and SPO type printers, audio attachments and software can be ordered for these models. Available in Type A, D, B, C, DO, O, OO, and OOO. Supplied with batteries and AC adapter; one year warranty.

Rex Micro-A Durometers

The Rex Type M Micro-A scale Durometer was developed for customers who need to check specimens thinnner than the 1/4"required by the ASTM standard for durometer testing. It uses a much smaller indenter and lighter springload than the standard A scale gauge, enabling the user to check materials as thin as .050", yet still obtain readings comparable to the standard A scale. The Micro-A gives readings to approximately +/- 2 points of a standard A scale durometer. Since the correlation of readings between the Micro-A and the A scale is not exact, we recommend use with a Rex Test Block Kit (see below) for comparison purposes. The Micro-A is available in Model 1600M or digital DD-3M. Effective May 2000, the Type M gauges are now ASTM D2240 certifiable. To conform with the requirements of this revised standard, these durometers must be used in conjunction with a dampened operating stand with a controlled rate of descent. Please call.

Rex Type A Test Block Kit

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