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practice guide r e c o m m e n d e d N I S T
Rockwell Hardness Measurement of Metallic Materials

Samuel R. Low

960-5
Special Publication 960-5

NIST Recommended Practice Guide
Special Publication 960-5

Rockwell Hardness Measurement of Metallic Materials

Samuel R. Low
Materials Science and Engineering Laboratory January 2001

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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

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Certain commercial entities, equipment, or materials may be identified in this document in order todescribe 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) CODEN: NSPUE2 U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 2000 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

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FOREWORD

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The Rockwell hardness testcontinues 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 Rockwellhardness 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 highaccuracy is not as critical.

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ACKNOWLEDGMENTS ...........................................................

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-TECCorporation 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 wouldalso 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.

* The acknowledgements of the persons and companies listed above should not be interpreted as an endorsement by NIST of theirproducts or services. v

Table of Contents N
List of Figures ..................................................................................... ix Tables List of Tables ...................................................................................... xii 1. Introduction .................................................................................... 1 Test 2. Rockwell Hardness Test...