Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

NIST Recommended Practice Guide: Installing, Maintaining, and Verifying Your Charpy Impact Machine



D P. Vigliotti, Thomas A. Siewert, Christopher N. McCowan


The quality of the data developed by pendulum impact machines depends on how well the machines are installed, maintained, and verified. This is the reason that ASTM Standard E23 Standard Test Methods for Notched Bar Impact Testing of Metallic Materials specifies annual direct and indirect verification tests. Each year, NIST provides reference specimens for indirect verification of over 1000 machines around the world. From evaluation of the absorbed energies and the fractured specimens, we attempt to deduce the origin of energies that are outside the ranges permitted by Standard E23, and report these observations back to the machine owners. This recommended practice summarizes the bases for these observations, and hopefully will allow machines to be maintained at higher levels of accuracy. In addition, we provide details of the NIST verification program procedures and the production of the specimens.
Special Publication (NIST SP) - 960-4
Report Number


absorbed energy, charpy v-notch, impact test, machine repair, misalignment, mounting, pendulum impact test, verification testing, worn anvils


Vigliotti, D. , Siewert, T. and McCowan, C. (2000), NIST Recommended Practice Guide: Installing, Maintaining, and Verifying Your Charpy Impact Machine, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed May 27, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created October 1, 2000, Updated November 10, 2018