Automotive Medical Packaging CNC Milling Non-standard Parts

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Comparison of Several Anti-loose Nuts Used in the Car

1. Normal hexagonal head nut.

Ordinary hexagonal head bolts, nuts production volume, mature technology, low cost, will still be the mainstream of automotive fasteners. Over the years, many fastener manufacturers are committed to the study of thread anti-loose, but also for ordinary hexagonal bolts, nut looseness issues made a special analysis, focusing on the analysis of ordinary hexagonal head nuts in the manufacturing process to affect the pretension force factors, the main reasons for the impact of pretension force is tooth shape, coefficient of friction, etc. , preliminary analysis, for the general standard thread, thread bite when most of the load concentrated on the thread surface of the first and second teeth, and friction coefficient Users often have misconceptions that the greater the friction, the better. In fact, otherwise, the smaller the coefficient of friction between the friction side, the greater the axial clamping force, the better the fastening performance. According to the change of friction coefficient, the influence of tightening efficiency and fastening degree is the theory of "scissors difference" change trend, and through test and verification, the "median" coefficient of friction is used, that is, smaller than the friction coefficient of the current bolts and nuts, which we call the small coefficient of friction. And mass production, all parts to maintain a fixed value is not possible, through joint design with suppliers public relations, improve the process, as far as possible to maintain the coefficient of friction generally fluctuates within a reasonable range.

2. Never loosen the nut.

Fasteners produced by many companies claim never to loosen, such as the DTFLOCK lock nut in the United States, the HARDLOCK lock nut in Japan, the DISC-LOCK anti-loose washers in the United States, the NORD-LOCK anti-loose washers in Sweden, and so on. By comparing the final selection with the trial small coefficient of friction nut, the DTFLOCK lock nut and Japan's HARDLOCK lock nut.

1) DTFLOCK nut.

The DTFLOCK nut has a 30-degree wedge bevel at the bottom of the inner thread, and when the bolts and nuts are tightened, the tip of the bolt is tightly mounted on the wedge slope of the nut, resulting in a great deal of locking force. Due to the change of angle of the tooth shape, the normal force generated by the contact between the threads is applied to the bolt shaft at an angle of 60 degrees (see Figure 2), rather than the 30 degree angle like the normal thread, the DTFLOCK threading pressure is much greater than the fastening pressure, therefore, the resulting anti-loose friction force is bound to be greatly increased.

2) HARDLOCK nut.

HARDLOCK is a double nut (see Figure 3), the outer side of the inner nut is equipped with eccentric protrusion, the outer nut is a common nut structure, its inner side is equipped with concentric grooves, the outer side of the inner nut when the outer nut is ready for tightening is different from the bolt, the eccentric protrusion of the inner nut and the bolt is tightened by the outer nut to produce radial force, equivalent to the addition of tugs in the thread gap, thread all-round tightening.

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