Hardness Testing

NIST Recommended Pratice Guide - Special Publication 960-5
Samuel R. Low

Materials Science and Engineering Laboratory

January 2001

U.S. Department of Commerce
Donald L. Evans, Secretary
Technology Administration
Karen H. Brown, Acting Under Secretary of
Commerce for Technology
National Institute of Standards and Technology
Karen H. Brown, Acting Director

Certain commercial entities, equipment, or materials may be identified in
this document in order to describe an experimental procedure or concept
adequately. Such identification is not intended to imply recommendation or
endorsement by the National Institute of Standards and Technology, nor is it
intended to imply that the entities, materials, or equipment are necessarily the
best available for the purpose.

National Institute of Standards and Technology
Special Publication 960-5
Natl. Inst. Stand. Technol.
Spec. Publ. 960-5
116 pages (January 2001)
For sale by the Superintendent of Documents
U.S. Government Printing Office
Internet: bookstore.gpo.gov Phone: (202) 512–1800 Fax: (202) 512–2250
Mail: Stop SSOP, Washington, DC 20402-0001



The Rockwell hardness test continues to be applied as a tool for assessing
the properties of a product while the tolerances on the acceptable material
hardness have become tighter and tighter. Adhering to “good practice"
procedures when performing Rockwell hardness measurements and
calibrations is a beneficial step to reducing measurement errors. The purpose
of this Guide is to explain the causes of variability in Rockwell hardness test
results and to supplement the information given in test method standards with
good practice recommendations. Although this Guide is directed more towards
the users of Rockwell hardness having the greatest concern for accuracy in
their measurements, much of the information given is also applicable for users
that only require test results to be within wide tolerance bands, where high
accuracy is not as critical


The author would like to thank the following persons for sharing their
experience and providing information for this Guide. Their input and review
has provided a link to the practical world of Rockwell hardness testing.*
T. Robert Shives , Consultant
Richard Antonik , SUN-TEC Corporation
Robert A. Ellis and Richard A. Ellis, David L. Ellis Co., Inc.
Thomas P. Farrell , Mitutoyo America Corporation
Giancarlo Mazzoleni and Douglas B. McGhee, Newage Testing
Instruments, Inc.
Michael L. Milalec and Richard J. Snow , Gilmore Diamond Tools, Inc.
Paul M. Mumford , United Calibration Corporation
Edward L. Tobolski , Wilson Division of Instron Corporation

The author would also like to thank present and former NIST co-workers
James L. Fink, Carole D. Flanigan, Robert J. Gettings, Walter S. Liggett, Jr.,
David J. Pitchure, John H. Smith, and John Song for their contributions towards
the Rockwell hardness standardization program at NIST