Analysis on the Causes of Sliding Wire of Self-tapping Screws

What is the reason for the frequent slippage of self-tapping screws at the connection?

Improper selection of the hole diameter of the screw may cause slippage. The processing range of the major diameter d1 value of the self-tapping screw is 4.22~4.04mm.

And the processing range of the minor diameter d2 value is 3.10-2.95mm, so the value of the self-tapping screw aperture must fall between 4.22-2.95mm.

In order to increase the occlusal force between the screw thread and the steel plate, while considering the impact of the increase in the thickness of the steel plate on the screw penetration resistance.

The small value of the hole diameter is generally 3.1, and the large value is generally 3.5.

When the matching hole is too large, the bite of the screw thread and the steel plate is too small, and slippage is easy to occur; when the matching hole is too small, the screw is not easy to penetrate.

At the same time, screw breakage will occur; therefore, for steel plates of different thicknesses, different screw holes must be selected to avoid slippage.

The unreasonable design of the screw hole structure can easily cause slippage.

The screw hole structure can be divided into flat holes and flanged holes. Through research, the steel plate with a thickness of less than 1.0mm must use flanging holes.

Structural defects of screws can easily cause slippage. The structural defects of the screw include thread size and diameter not up to standard, pitch value not up to standard, thread angle not up to standard, unsaturated and incomplete thread, and inverted taper in thread.

The large diameter of the screw is too small and the small diameter remains unchanged will affect the unilateral occlusion of the screw and the steel plate.

And the small diameter of the small diameter and the large diameter will also affect the unilateral occlusion of the screw and the steel plate.

Pitch value P of self-tapping screws is 1.4mm. When this value is too large, it means that the helix is ​​elongated and the length of the thread “biting” into the steel plate is too short, which will also cause slippage.

The thread angle of the self-tapping screw is 60℃; under the condition of the same size and diameter, the thread will be fuller and firmer when the thread angle is too large,

Which is beneficial to the occlusion with the steel plate and can increase the screwing torque.

But it can’t be too big for wireless, so the screw teeth become blunt, which will affect the penetration ability. Generally 60-65° is suitable.