MIL-DTL-18240F

Abstract

This specification defines the requirements for self-locking elements for use in externally threaded fasteners such as bolts and screws to be used in fasteners with either UNC, UNJC, UNF, UNJF, UNRC or UNRF threads and where the temperatures will not exceed 250&#176;F. <br>This specification includes three types of self-locking elements as follows: </span><pre> Type N.....Plug/Pellet Type L.....Strip Type P.....Patch</pre> <br> <strong>Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of use in improving this document should be addressed to: Commander, Naval Air Warfare Center Aircraft Division, Code 414100B120-3, Highway 547, Lakehurst, NJ 08733-5100, by using the Standardization Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter.</strong> <br><b><u>Intended Use:</u></b> The self-locking elements covered by this specification are intended to be incorporated in external screw threads to be used in applications where maximum temperature does not exceed 250&#176;F. When these self-locking elements are incorporated in external threads and are used in compliance with MS15981, all the configurations of <a>figure 1</a> are interchangeable Type N element, plug/pellet configuration is intended to be installed via a hole drilled into the fastener. Type L element, strip configuration is intended to be installed via a strip cut through the threads parallel to the length of the fastener. Type P element, patch configuration is intended to be installed without removal of any material of the fastener. A specific type should be specified only when required by design or application requirements. The prevailing-torque values given in this specification are conformance requirements for self-locking elements and apply only to the combination of test conditions described in the locking torque test procedure. If the conditions of the actual service application differs from those of 4.4.2 (e.g. internally threaded hole in a different material, length of thread engagement, class of internal thread tolerance, speed of driving, different plating or coating on screw or mating part) the prevailing-torque values may vary. Such values can only be determined through testing the locking element in its application. The plug/pellet is not recommended for sizes below .190. From Configurations listed in Revision D dated 25 February 1972 <pre> Configuration A plug/pellet type superceeded by Type N Configuration B strip type superceeded by Type L Configuration B patch type superceeded by Type P</pre> <br>