Hardness testers 1

[Elastomatt]

Hi,

I run a QA lab and we have an old Wallace Microhardness (IRHD) tester. It is hand operated and at least 20years old. I would like to replace it and wondered if anyone can suggest the best (or most commonly used) meter.

Are there any disadvantages/limitations with newer machines

Thanks

Elastomatt

 

[tom1953]

In the US, the most common hardness measurement is Durometer hardness, commonly known as Shore Hardness. The "A" scale is used for typical rubber hardnesses, "D" for hard materials.

See

http://www.instron.us/wa/applications/test_types/hardness/shore.aspx

Tom Jablonowski, TSE Industries, Inc.

http://www.tse-industries.com

 

[corrosionman]

Why not contact the manufacturer of your old tester and get it recalibrated - - or obtain a few specimen pieces of known hardness and recalibrate it yourself ( We did on our 25 yr old testers which was in a box complete with an allen key to help do the job.)
Cheers
Corrosionman.

 

[Elastomatt]

Hi Guys,

Thanks for the info. we do use Shore A meters as well, some are handheld and I don't like them as the results seem variable (control of force).
Most of our customers now have more modern equipment and there have been some differences between our test results recently. I have had our machine checked out (by our materials lab manager) using the calibration pieces it was OK.
I will give Wallace a call and see what they have to offer, they do our annual calibration already.

Elastomatt

 

[GrahamBennett]

You need a bench-mounted deadload hardness tester for the most accurate results. Handhelds are notoriously inaccurate. Microhardness testers are only useful for test pieces that are thinner than a specified 6mm (1/4") hardness button.

 

[Elastomatt]

Thanks Graham, I will look into that. Most of our samples are below 6mm (2.0 ± 0.1mmm), they are prepared from the producr using a splitting machine.
However we do check directly on product which have varying profiles, what is the maximum size dead load bench-mounted testers can take? And is there anything to be aware of (i.e. curved surfaces against flat)?

Thanks

Elastomatt

 

[GrahamBennett]

Maximum size of sample depends on the length of the rod that supports the hardness tester but I would say somewhere in the region of a 30-40mm sided cube. Don't measure the hardness on a convex surface, as the sample will bend under the load causing a lower hardness reading. If you have to measure on a curved surface make sure it's concave.

You can always ply up 3 or 4 piecces of your sheet/part/whatever and use this for testing the hardness (but the result won't be quite as accurate).