u/Such_Technician_5476

Tang’s thread is a specialized, dual-directional fastener design engineered to prevent nuts from backing off under extreme vibration by integrating both a right-hand and a left-hand thread onto a single shaft. Unlike traditional fasteners that loosen along the exact same helical path used to tighten them, this configuration redirects the energy of vibrational stress; as a result, when vibration forces the front nut to back off, that loosening force transfers directly into a rear locking nut, driving it deeper and instantly jamming the two nuts against each other. This self-locking mechanism—where more shaking actually results in a tighter connection—is critical for high-stakes, extreme-vibration environments like high-speed rail joints, spacecraft components, and heavy industrial machinery. However, because Tang threads require exceptional manufacturing precision, engineers also rely on alternative vibration-resistant designs. These include wedge-locking assemblies like Nord-Lock, which use interlocking cams to increase tension under movement; wedge ramp threads like Spiralock, which feature a 30-degree ramp at the thread root to maintain continuous metal-to-metal contact; and prevailing torque nuts, which utilize nylon inserts or deformed threads to tightly grip the bolt and resist rotational backing through heavy friction: https://alltin-fastener.com/article/164/detail/4.html

Research Article: https://www.mdpi.com/2076-3417/13/24/13253

The Use of Two Nuts to Prevent Self Loosening: https://www.boltscience.com/pages/twonuts.htm