An improved locking nut comprises (1) an internally threaded shell, partly resembling a conventional nut, that can be engaged by a wrench or other tool, and (2) an internally and externally threaded insert that engages the threads of the shell and a bolt. Whereas some prior locking nuts are plated over their entire surfaces for lubrication and prevention of galling caused by engagement of threaded surfaces, this nut includes plating (silver or other soft material) only on the threaded surfaces of the insert, which, during engagement, are enclosed. The elimination of external plating reduces the likelihood of contaminating adjacent equipment.

The insert makes an interference fit with the bolt thread, helping to lock the shell against loosening during vibration. In response to bolt tension upon tightening, the insert undergoes slight elongation that helps distribute the tension along the full length of thread engagement. The locking nut helps to dissipate vibrational energy through microscopic frictional rubbing between the threads of the insert and the threads of the shell. The soft plating may contribute to damping of vibrations. Rounding of the outer end of the shell reduces the potential for damage to nearby equipment or injury to nearby persons.

This work was done by Rahmatollah F. Toosky and Scott Forest of McDonnell Douglas Corp. for Johnson Space Center. For more information, download the Technical Support Package (free white paper) at under the Mechanics/Machinery category.

Title to this invention, covered by U.S. Patent No. 5,860,779, has been waived under the provisions of the National Aeronautics and Space Act {42 U.S.C. 2457 (f)}. Inquiries concerning licenses for its commercial development should be addressed to:

McDonnell Douglas Corp.,
A wholly owned subsidiary of The Boeing Co.
PO Box 2515
Seal Beach, CA 90740-1515

Refer to MSC-23062-1, volume and number of this NASA Tech Briefs issue, and the page number.

NASA Tech Briefs Magazine

This article first appeared in the August, 2010 issue of NASA Tech Briefs Magazine.

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