How to Measure Shore Hardness with the PosiTector SHD

Referenced products:

DeFelsko's PosiTector SHD Shore Hardness Durometer is designed for testing the hardness of non-metallic materials such as soft rubbers, rigid plastics, and super soft gels. The PosiTector SHD features and easy-to-read digital display, internal memory, and a user-adjustable measurement timer with on-screen countdown.

What is Material Hardness?

Material Hardness is a measure of a material’s ability to withstand deformation such as bending, scratching, abrasion, or cutting. Measuring strength and durability is a crucial element of Quality Assurance and Quality Control. Often, a material is required to meet a specific standard of hardness—often determined by testing Shore Hardness.

Indentation hardness testers such as the PosiTector SHD Shore Hardness Durometer and the PosiTector BHI Barcol Hardness Impressor use a precisely-shaped tip, or indentor, connected to a calibrated spring, and measure how far the tip penetrates into the material. The greater the indentation, the softer the material.

What is Shore Hardness?

Over 100 years ago, Albert Ferdinand Shore invented the Shore durometer, which offered different scales for measuring the hardness of different materials such as thermoplastic elastomers, vulcanized (thermoset) rubber, elastomers, soft gels, and hard plastics. Testing Shore hardness is a quick way to determine how a material will behave against impact and abrasion. Shore D Hardness Durometers are also commonly used to establish whether a coating has cured sufficiently.

ASTM D2240—Standard Test Method for Rubber Property—Durometer Hardness, identifies twelve different durometer scales: Types A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R. The different scales apply to materials with different properties.

Table detailing different Shore Scale types and their corresponding materials types

What is a Shore Hardness Durometer?

Photo of a stand-alone PosiTector SHD Shore Hardness Durometer
PosiTector SHD

A Shore Hardness Durometer is an instrument consisting of a precisely machined indentor, calibrated spring, pressor foot, and a display (analog or digital) used to measure the hardness of a material. When the indentor is forced into a material, under specified conditions, a Shore hardness value is determined by the inverse of how far the indentor was able to penetrate.

The two most common scales for measuring shore hardness are Shore A and Shore D. They have slightly different measurement configurations—each with a different indentor shape and different spring loads.

  • Type A: Per ASTM D2240, the Shore A indentor is a hardened steel rod with a 35° angle truncated cone used for testing the hardness of softer materials such as flexible mold rubbers and other soft polymers.
    *See the PosiTector SHD A
  • Type D: Per ASTM D2240, the Shore D indentor is a hardened steel rod with a 30° angle conical point that is used to test the hardness of hard, highly resistive materials such as thick vinyl and rubbers.
    *See the PosiTector SHD D

Shore Hardness is best measured with a hand-held electronic instrument, like the PosiTector SHD. A simple, easy-to-read digital display takes the guess-work out of analog scales.  It has internal memory and free desktop software that help to make reporting easy. HiLo alarms, Statistics mode, and Auto Ignore mode also make quality control easier than ever.

How is Shore Hardness measured?

The digital PosiTector SHD Shore Hardness Durometer is a hand-held hardness tester built to minimize the chance of operator error. These instructions are written for the PosiTector SHD but can be used with any hand-held (manual) Shore hardness durometer.

Step 1: Identify a Test Location

The Shore hardness durometer should be used on a hard, firm surface. If the material is thin or otherwise likely to deform, place it on a firm surface for the duration of the test.

The measurement points should be at least 6mm (0.24”) apart.

Step 2: Take a Measurement

Press the probe down firmly onto the material to be measured until the indentor foot is in full, flat contact with the surface and hold steady. The test timer will begin counting down. When the timer reaches 0s, the gage will beep twice and display the measurement value.

How to Verify the Accuracy of a Shore Hardness Durometer

Before and after each work shift, check the accuracy of the durometer with the included test blocks. Place the test block on a hard, flat surface. To achieve the most accurate Shore hardness measurement press down firmly with the PosiTector SHD A or the PosiTector SHD D on each test block and take 3-5 readings ensuring measurement points are at least 6mm (0.24”) apart.

What are the Benefits of using a digital PosiTector SHD A or PosiTector SHD D Shore Hardness Durometer?

Digital Readout

The easy-to-read digital display helps take the guesswork out of reading analog scales, reducing the chances of operator error.

Memory, Statistics, and USB Port

The PosiTector SHD features internal memory storage for recording data. The on-screen statistics mode continually displays/updates while measuring shore hardness. When the measurement is complete, stored readings and graphs can be found using the built-in USB port to download readings to a PC or Mac.

Free Software Solutions

To report and store Shore hardness readings, DeFelsko offers free solutions to view and analyze measurement data. Using DeFelsko’s PosiSoft Solutions, select from our desktop version, an easy-to-use mobile app, or PosiSoft USB—a simple gage interface similar to a flash drive.

Learn more about PosiSoft Solutions.

Test Timer

When measuring the hardness of a material, the PosiTector SHD features an on-screen timer. The timer will automatically start counting down once the indentor is pressed firmly down. When the time (typically 3 seconds) elapses, a measurement is taken.

Continuous Readings

Continuous Reading mode is ideal when a test timer is not required or when performing a calibration verification. When enabled, the PosiTector SHD will continuously display Shore hardness readings.

Statistics Mode

Readings and statistics can be recorded into memory for further analysis and reporting. The average, standard deviation, and min/max hardness statistics are continually updated and displayed while measuring with the PosiTector SHD.

HiLo Alarm

The HiLo Alarm on the PosiTector SHD allows the gage to audibly and visibly alert the user when the readings exceed user-specified limits.

Auto Sub-Batch

In the Advanced model of the PosiTector SHD, the Auto Sub-Batch automatically creates a new sub-batch after the necessary number of readings are stored.

What Test Standards Exist to Measure Shore Hardness?

The following standards are used to determine the Shore hardness of a material.

ASTM D2240—Standard Test Method for Rubber Property—Durometer Hardness

ASTM D2240 guides the user through measuring the hardness of soft rubbers. It defines proper techniques and procedures for measuring soft rubbers identifying twelve types of measurement.

“1.1 This test method covers twelve types of rubber hardness measurement devices know as durometers: Types A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R. The procedure for determining indentation hardness…”

“4.1 This test method is based on the penetration of a specific type of indentor when forced into the material under specified conditions.”

ASTM D2240 Test Procedure with the PosiTector SHD

  1. Place the specimen on a flat, hard, horizontal surface to provide for positioning and stability.
  2. Apply the presser foot to the specimen with sufficient pressure to assure firm contact. Press downward with a firm, smooth action that will help avoid sliding or scraping that could result in an erroneous reading and may damage the probe tip.

Refer to the ASTM D2240 for a complete description of the test standard.

ISO 48-4:2018 Rubber, vulcanized or thermoplastic—Determination of hardness—Part 4: Indentation hardness by durometer method (Shore hardness)

"This first edition of ISO 48-4 cancels and replaces ISO 7619-1:2010 which has been technically revised."

Per ISO 48-4, to measure the hardness of a rubber with a durometer (Shore hardness) relies on the response of the rubber to an applied indentation. The response varies and depends on many factors.

Refer to the ISO 48-4:2018 for a complete description.

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