Self-tapping screws are in the metal or non-metallic materials in the pre-drilling hole in the self-drilling with a female thread with a threaded fastener. Self-tapping screws have the characteristics of high tension, single piece, unilateral combination. With high pull, single, unilateral combination of features. Self-tapping screws are used for connection between thin metal plates (steel plates, saw boards, etc.). When connecting, first thread the bottom of the connector, and then screw the tapping screw into the threaded bottom hole of the connected part. As the tapping screw thread surface has a high hardness (≥ 45HRC), can be connected to the threaded bottom hole in the internal thread, so as to form a connection.
Although there are many types of tapping screws, but they have the following main features
(1) are generally made of carburized steel (99% of the total product). Can also be made of stainless steel or non-ferrous metals.
(2) The product must be heat treated. Carbon steel tapping screws must be carburized, stainless steel tapping screws must be hardened by solution. So that the tapping screw to meet the standard requirements of the mechanical properties and performance.
(3) product surface hardness is high, good core toughness. That is, "inside the soft outside just". This is a major feature of self-tapping screw performance requirements. Such as the surface hardness is low, not into the matrix into the matrix; such as the core toughness is poor, a twist on the broken, can not be used. So "within the soft outside just" is the self-tapping screw to meet the performance requirements.
(4) the surface of the product are required surface treatment, the general plating treatment. Some products surface by phosphate treatment (phosphate). Such as: wall plate self-tapping screws are mostly phosphating.
(5) the use of cold heading process production. Recommended high-speed cold heading machine and high-speed rolling machine or high-speed planetary roller machine production to ensure product quality. This is the production of self-tapping screw head shape is good, high quality thread.
Self-drilling tapping screws and ordinary tapping screws is different from the ordinary tapping screws in the connection, to be drilled (drilling through the bottom hole) and tapping (including fastening connection) two processes; and self-drilling When the screw is connected, the drilling and tapping processes are completed once. It is first drilled with a drill bit in front of the screw, then tapped with screws (including fastening connection), saving construction time and improving construction efficiency.