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Technical Information

Principles of the DTFLOCK Thread Locking Technology    

       All types of machines and sub-assemblies will use fasteners during connecting or assembling operation. Fastener brings convenience to machinery industry, but it has an unavoidable weakness, i.e. it becomes loose on its own during excessive vibration and thus lead to damage or disassembly of a component or a complete set of equipment, or even a severe accident.

      In order to solve the fastener loosening problem, many scientists and engineers in different countries have conducted extensive tests and researches. They took different kinds of measures such as locking pieces, pins, nylon inserts, deformed threads, chemical adhesives, etc. These approaches can prolong to some extent, the service life before the fastener gets loose. But the fastener loosening problem has not been fundamentally eliminated.

The thread form has an important influence on threaded fastener loosening. For this, US engineers redesigned geometrical shape of the thread form after studying the shape and the load conditions of fastener thread, and invented the current “DTFLOCK” thread technology. Since then, the fastener loosening problem has been completely resolved.

    The reason why DTFLOCK fastener can effectively prevent thread from loosening is due to its unique structure. There is a 30° wedge ramp at the root of the female thread. When the bolt and the nut are tightly engaged, tooth crest of the bolt thread will press tightly against the wedge ramp of the DTFLOCK thread and thus generate large locking force. Due to change of the thread angle, the angle between the normal force generated at the thread pair and the bolt axis is now 60° instead of 30° with an ordinary thread. Obviously, normal force of the DTFLOCK thread is far greater the fastening force. So, the anti-loosening friction force generated by this normal force will become much greater (See Fig.1).         

                             Fig. 1  DTFLOCK thread form and Standard thread form

      For the ordinary threads, the first two engaged threads bear 70-80% of the total load. The other engaged threads bear only a small fraction of the total load. So, under vibrating working loads, fastener with ordinary thread form can easily overcome the locking force generated on the contacting surface and thus generate relative turning. Then the thread will become loose.

      For DTFLOCK threads, due to its unique structure, crest of each bolt thread press tightly against the 30° wedge ramp. The load can be evenly distributed among all engaged threads. So the load can be evenly distributed to each contacting surface or point, and different parts of the thread can generate almost the same anti-loosening friction force. It can withstand transverse vibration. So, problems such as loose thread or thread stripping, etc. can be eliminated. In addition, fatigue strength of the thread can also be greatly improved.

      The transverse load vibration test was conducted with a Junkers vibration tester in the laboratory confirmed that the DTFLOCK thread presents outstanding anti-vibration capability (see Fig.2). They tested 3 types of nuts, i.e. ordinary standard nut, effective torque locking nut and DTFLOCK nut. Each nut was tested for 2 minutes with the same standard bolt, the same tightening torque, the same vibration amplitude and frequency, and the same vibration tester in the same laboratory. The test result was: ordinary standard nut became loose very quickly and lost all its locking capability, effective torque locking nut lose 70% of its locking capability, while DTFLOCK nut maintained its locking capability during the whole test duration. 

      Besides, further transverse vibration tests were conducted to test the reusability of the three types of thread. The test result was: the DTFLOCK self-locking nut has good reusability since it can maintain its locking force and locking performance after repeated screwing and unscrewing, while ordinary nut and effective torque locking nut may gradually lose its locking force and locking capability after several times of screwing and unscrewing.

Fig. 2     Vibration testing results of the 3 types of nuts

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