What are the characteristics and defects of ordinary self-tapping locking screws?

Ordinary self-tapping locking screws are generally dedicated self-tapping locking screws for specific materials. For plastic parts with high hardness and brittleness, flat-tailed self-tapping locking screws or triangular tooth locking screws have been developed (referred to in the industry as BTT tooth self-tapping locking screws, PTT tooth self-tapping locking screws); For some soft plastics, self-tapping locking screws or triangular screws with pointed tails have been developed. Aiming at the characteristics of high hardness and good ductility of iron parts, special triangular teeth locking screws have been developed.

Both BTT thread self-tapping locking screws and pointed-tail self-tapping locking screws are self-tapping thread threads and the screw cross section is triangular. The screw must be heat treated after processing; BTT self-tapping locking screws and pointed-tail Self-tapping locking screws belong to the mechanical tooth type, and the screws must be heat treated after they are formed. The purpose of heat treatment after the self-tapping locking screw is formed is to change the metallographic structure of the screw, so that the surface hardness is higher, the core hardness is soft, and the screw shaft has a certain toughness while having a harder thread.

Due to the significant differences in the physical properties of plastic and iron, iron has high strength and good thermal conductivity; while plastic is brittle and has poor thermal conductivity. Obviously, the special white tapping locking screw developed specifically for plastic or iron does not have the versatility between the two locking materials of plastic and iron; under the same tightening torque, the special self-tapping locking screw for iron Screws are easy to damage the plastic parts when locking the plastic parts, causing the screw to slip; on the contrary, under the same tightening torque, the special self-tapping screw for the plastic parts is locked due to the large screw angle when the iron parts are locked. , It is easy to cause phenomena such as failure to lock into the iron hole or damage to the screw thread.zinsn.com