Although there are many kinds of self tapping screws, they all have the following main characteristics:
(1) Generally, it is made of carburized steel (accounting for 99% of the total products). It can also be made of stainless steel or non-ferrous metals.
(2) The product must be heat treated. Carbon steel self tapping screws must be carburized and stainless steel self tapping screws must be solution hardened. In order to make the self tapping screw meet the standard requirements of mechanical properties and performance.
(3) The surface hardness of the product is high and the core toughness is good. That is, "soft inside but firm outside". This is a major characteristic of self tapping screw performance requirements. If the surface hardness is low, it can not be screwed into the matrix; if the core toughness is poor, it will be broken after screwing, and it can not be used. Therefore, "soft inside and hard outside" is self tapping screw to meet the performance requirements.
(4) The surface of the product needs surface protection treatment, generally electroplating treatment. Some products need phosphate treatment (phosphating). For example: the wallboard self tapping screws are mostly phosphatized.
(5) It is produced by cold heading process. High speed cold heading machine, high speed thread rolling machine or high speed planetary rolling machine are recommended to ensure product quality. The head of self tapping screw produced in this way has good shaping and high thread quality.
