30° wedge-shaped thread to prevent loosening of threaded fastener structure

The threads of threaded fasteners are mostly the tooth form angle of 60°, and the flank angle is symmetrical 30°. It is calculated according to GB16823.2-1977 (General Rules for Tightening of Threaded Fasteners), please pay attention to the micro-machinery commune Thread friction; thread frictionu003dFfμssesα/, where Ff is the bolt axial force, μs is the thread friction coefficient, α/-flank angle, ordinary thread α/u003d30, at this time thread frictionu003d1.154Ffμs. Because the thread friction is small, the nut is prone to self-rotating looseness when the nut is subjected to vibration.

The first fastening member with external thread, and the second fastening member with internal thread, the first fastening member and the second fastening member cooperate with each other through the external thread and the internal thread; the second fastening member The internal thread is an asymmetrical shape, the flank angle of the first side surface of the internal thread is 60° or approximately, and the flank angle of the second side surface of the internal thread is 30° or approximately. The first fastening member is a bolt 1, and the second fastening member is a nut 2. The bolt 1 is provided with a male thread 3, and the nut 2 is provided with a female thread 4, and the bolt 1 and the nut 2 are matched with each other through threads. The female thread 4 of the nut 2 has an asymmetrical shape, the flank angle of the first side surface 5 of the female thread 4 is 60°, and the flank angle of the second side surface 6 of the female thread is 30°. Among them, the first side surface 5 is a bearing surface. When the bolt 1 and the nut 2 are tightened to each other, the tooth tip 7 of the bolt 1 abuts on the first side surface 5. The second side surface 6 is a non-load-bearing surface. When the bolt 1 and the nut 2 are tightened to each other, the tooth tip 7 of the bolt 2 does not contact the first side surface. (Guide: The advantages and disadvantages of fixing the stadium fence by expansion screws)

For ordinary threaded fasteners, the tooth profile angle is 60°, the arrow represents the direction of axial force, and the axial force is Ff. It can be seen that because the tooth profile half angle of ordinary threaded fasteners is 30°, the thread friction force u003d 1.154Ffμs. For a threaded fastener with a 30° wedge thread, as shown in the figure, the flank angle on one side of the female thread of the thread is 60°, and the flank angle on the other side is 30°, and the arrow represents the direction of axial force.

Ordinary 60°thread

When the bolt and the nut are tightened with each other, the tip of the bolt is tightly pressed against the flank of the female thread with a flank angle of 60°, because the thread friction u003d Ffμssesα/, at this time α/u003d60° , That is, thread friction u003d 2Ffμs, which is 1.733 times that of ordinary thread. The increase of thread friction produces a great locking force, which makes the nut not easy to spin and loosen, thus forming a good self-locking ability.

The Junker transverse vibration testing machine is used in the laboratory to do transverse vibration test. Through comparison with ordinary threaded fasteners, it shows the excellent anti-vibration ability of threaded fasteners that prevent loosening of 30° wedge threads. Curve A is the anti-vibration curve of the nut with 30° wedge thread; curve B is the anti-vibration curve of ordinary threaded fasteners. When using the same bolt, the same amplitude, frequency, and the same tightening force, on the same testing machine, when the time is controlled for two minutes, the ordinary nut completely loses the locking force, while the nut of this embodiment is in the two-minute test period. The self-locking ability is still maintained.

More related stamping hardware industry news: