Direct Verification of Threaded Fastener Locking Compounds and Adhesives
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This article explores the feasibility of a method to directly verify that thread lock compound or adhesive has cured sufficiently to provide secondary locking. The application of a torque after assembly and cure time was found to provide a viable verification test. Fastener material and coatings were found to significantly affect cure. For example, medium-strength anaerobic compound used with fasteners made of inactive material such as stainless steel had curing issues which prevented determination of a useful verification test torque. However, modifications such as higher-strength compound or primer can be introduced making this method viable even for fasteners made with inactive materials and coatings. This article outlines a process to implement this method in practice. This requires sample tests with representative product to determine a test verification torque. This process is particularly useful in identifying curing and locking performance issues, and provides guidance for modification so that the method can be successfully implemented in practice. Test results show that application of verification test torque with or without standard vibration test exposure does not degrade the locking performance.
KeywordsFastener Thread lock compound Loosening Thread adhesive Prevailing torque Secondary locking Verification method Locknut
- 1.CxP 70135: Constellation Program Structural Design and Verification Requirements, NASA (2008)Google Scholar
- 2.Light, D.J.: Vibration loosening of threaded fastenings. CME 30, 56–60 (1983)Google Scholar
- 4.Haviland, G.S.: Machinery Adhesives for Locking, Retaining and Sealing. Dekker, New York (1986)Google Scholar
- 5.NASM1312-7: Fastener Test Methods, Method 7, Vibration, National Aerospace Standard (1997)Google Scholar