Chinese Ministry of Railways is the first to introduce the technology of 30° variable tooth type thread. With the successful application of this technology in railway locomotives and rail, the Ministry of Railways issued a TB / 3019 standard in 2001.
      Typical parts of 30° variable tooth type locking thread technology successfully used in railway locomotive is locomotive brake systems. The brake disc and the brake pads is a group of parts within the locomotive brake systems, the braking performance directly affects the driving safety of the train. In the past using ordinary fastener connection, the locking performance is not reliable after several tests. June 2002, Nanjing, China Non-metallic Minerals Industry Corporation friction materials testing center conducted a brake test about Dongfeng 11 machine brake wheel-mounted brake discs and tablets on the brake test bench in a ratio of 1: 1. The coupling nuts of the test all used 30° variable tooth type locknut, test results proved that the friction coefficient of the test locomotive brake discs and brake pads t is stable and reproducible. Parking brake at the speed of 160km / h one time, the temperature of brake disc can reach 252 ℃, and the surface temperature of brake disc is up to 310 ℃, the entire testing process does not have a loosening of bolts and nuts. Laboratory test results and the actual results have both proved that the 30° tooth type locknut is reliable at temperatures above 300 ℃ and show excellent anti-loosening performance. 30° variable tooth type locknut is used in conjunction with standard threaded bolt, easy accessibility, can be reused more than ten times. Comparing with slotted nut, wire thread, double locking nuts and other connections, the new anti-loose way not only safe, reliable, but also easy to maintain the brake disc, you can save a lot of maintenance costs. Braking system is a key component of railway rolling stock, its working condition is very bad, the successful use of 30° variable tooth type locknut on the brake system promotes this technology widely used in railway locomotives.
      Mechanical Design which is edited by Professor Peng Weisheng and published by Higher Education Press tied the 30° variable tooth type locknuts and other four kinds of anti-loose screw connection technology which are metal prestressing nuts, opposite vertex nuts, nylon nuts and spring washers to the five locking technology. Mechanical design manual published by Chemical Publishing also do description about 30° variable tooth type locking screw technology and product standards.