Goddard Space Flight Center Tests Prove Preload Locking Internal Thread Form Withstands Random Vibrations of Space Shuttle Without Loosening

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Simple Changes to Design Improve Screw Thread Strength and Reusability

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Proving that a technology works is critical to acceptance in any industry. NASA was looking for a locking screw thread that could not only be implemented into a threaded fastener but into a threaded hole as well and it had to be reusable. Most orbit-bound space vehicles are completely assembled and dissembled 3 times before they are launched into space. This requirement coupled with the extreme operating temperatures called for a new self-locking fastener eliminated the conventional approaches to screw threads available at the time.

Successful independent testing by the Aerospace and Academic community is causing the self-locking threaded fastener to steadily gain fans across many industries. The thread form can be found in many applications were threaded fastener strength and reusability is a necessity such as: heavy truck and automotive powertrains, deep hole oil drilling equipment, high speed manufacturing equipment, and medical devices.

Referred to as the Preload Locking Internal Thread Form, the different geometry of the threaded fastener eliminates the shortcomings of the traditional female thread and improves the performance of the male thread. The difference in this thread form is that the traditional "V" shape of the thread has been modified to include a 3rd flank perpendicular to the trailing flank of the "V" shaped thread. This flank, sometimes referred to as the wedge angle or ramp angle, creates unified loading across all the mating threads. By reducing the high loading on the first few threads, significant yielding does not occur and the threads can be reused repeatedly. Also, the Preload-Locking Internal Thread Form can take advantage of thread enhancements. The thread form can also be manufactured by the cold form method and the shape of the thread allows for mating with male UNJ threads without modification.

Kevin Peacock is an Application Engineer for Spiralock Corporation in Madison Heights, MI. He has a Master's degree and over 20 years experience in fastener and machinery design. Spiralock Corporation is a "Fastening Solutions Company" serving the Transportation, Aerospace, Medical, Oil & Gas, and machinery industries.

For More Information Contact:
Spiralock Corporation
Cleve Lee
Portland House
21 Narborough Road
Phone: 44 (0) 1858 468646
Fax: 44 (0) 1858 466808

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