Re: hardness convertion

From: Jean-Marc Boéchat (
Date: Mon Dec 23 2002 - 18:46:17 EET

There's no way you will be able to convert Rockwell C into Shore D or A or backwards. The three scales are basically based on the
same principle: A penetrator is forced in the material with a given load for a certain time and the systems measures the depth of
the penetration. However the comparison ends right there.

For Rockwell C (HRC) the penetrator is a diamond cone with a tip radius of .2 mm and an angle of 120° the load is 1471 N.

For Shore A the penetrator is a steel pin with a conical flat tip and an angle of 35°, the load is 9.8 N whereas the Shore D has
a pointed steel pin with a 30° angle cone, a 0.1 mm tip radius and a load of about 49 N.

To be practical, let say that HRC is fit for hard materials like quenched and high yield steels, Shore A is used for rubber like
materials and soft polymers and Shore D is used for the more "technical" polymers.

It is the old oranges and apples story once again.

Have a nice and safe Holliday Season

J.-M. Boéchat

Rui Costa wrote:

> Hello list!
> Does anyone know where can I find a way to convert the Rocwell C hardness scale in to the Shore D and shore A hardness scale?
> Thank you in advanced and merry Christmas to all.
> With my regards,
> Rui Costa

Jean-Marc Boéchat               email:
MIM Systems Ltd                 phone:+4126 430 08 08  fax: +4126 430 08 09
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Disclaimer: "I speak for myself only, it's hard enough!"

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