Self-tapping screw structure
The self-tapping screws are composed of three parts: the head, the shank and the end of the shank. Each self-tapping screw has four major elements: the head shape, the wrenching method, the thread type, and the end type.
Head shape - a wide variety of head shapes. Round head (half-round head), Oblate head, Round head flange (with pad), Oblate head flange (with pad), Pan head, Pan head flange (with pad), Countersunk head, Semi-sinking head, Cylindrical head, spherical head, trumpet head, hex head, hexagonal flange head, hexagonal flange (with pad) and so on.
Twisting method - wrenching variety. External wrench: hexagonal, hexagonal flange, hexagonal flange, hexagonal, etc.; internal wrench: slotted, Phillips H, Phillips, Pozidriv, F-arranged. ,Scrulox, composite groove, internal spline, hexagonal flower shape (plum), internal triangle, hexagonal, inner 12 angle, clutch groove, six-vane groove, high torque cross slot and so on.
Thread type - a wide variety of threads. Self-tapping thread (wide thread), thread, drywall thread, fiberboard thread, and some other special threads. In addition thread can be divided into single lead (single head), double lead (double head), multiple lead (multi head) and high and low teeth double head thread.
The terminal type-end type mainly includes a saw end and a flat end. However, depending on the use of the function, grooves, grooves, cuts, or similar drill-shaped portions having a cutting function can be machined. In some standards, the same saw-end or flat-end, there are different forms.
From the above introduction, we can see that there are various changes in the shape of the head of the self-tapping screw, the wrenching method, the type of thread, and the type of the rod end. They can be combined with each other to express many different products that belong to the category of self-tapping screws.
Self tapping screw features
Self tapping screws main features
Although there are many kinds of self-tapping screws, they all have the following main features:
(1) Usually made of carburized steel (99% of the total product). 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 solid solution hardened. So that the self-tapping screws meet the standard requirements of mechanical properties and performance.
(3) The product has a high surface hardness and good core toughness. That is "inner soft outside just." This is a major feature of the self-tapping screw performance requirements. If the surface hardness is low, the screw cannot be inserted into the base body; if the core has poor toughness, the screw can be cut off and cannot be used. Therefore, "inner soft outer rigid" is a self-tapping screw to meet the requirements of the use of performance.
(4) The surface of the product needs surface protection, which is usually electroplating. Some products require phosphate treatment (phosphating). Such as: wall plate self-tapping screws are mostly phosphating.
(5) Cold heading process. It is recommended to use high-speed cold heading machines and high-speed thread rolling machines or high-speed planetary thread rolling machines to ensure product quality. The self-tapping screw head produced in this way is well formed and the thread quality is high.
Self tapping screw picture
Self-tapping screw expansion tube installation method
For the installation of self-tapping screw expansion pipe, some people say it is very simple, but if it is not properly installed, it will affect the installation effect of the product. For the installation of expansion pipes, we should first understand the weight of the items to be installed, the hardness of the mounting substrate, and then purchase a suitable expansion pipe. If the installation is a heavy object, a large-sized expansion pipe should be used. In addition, various lengths of products such as concrete, transfer bricks, perforated bricks, etc., can be purchased depending on the installation base material (installed wall material). It is necessary to use multiple expansion pipes of a relatively long size to install fixed objects, and determine the bearing weight based on the distance between the focal length and the focal point.
When installing the expansion pipe, first understand the size of the plastic expansion pipe, according to the size of the length of the same drill prefabricated hole (open wall hole with a power tool) opening size and expansion pipe diameter to one, the length should be longer than the total length of the expansion pipe 5mm-7mm. Then use the inner diameter to match the corresponding screw, such as the M8 expansion tube, the inner diameter of the inlet is 6, the smaller the more into the base material, if installed in the concrete, with 5mm expansion tube can be firmly installed, if used in the transfer Hard and solid wall materials such as brick, should use 6mm self-tapping screws supporting installation. The length of the screw is the total length of the expansion tube plus the thickness of the hanging tab + 5 mm.
Self-tapping screw sleeve installation method
There are two ways to install self-tapping screws:
Self-tapping screw sleeve installation method 1: When the number of installation is small, a simple installation method can be adopted. Specifically, a bolt and nut corresponding to the specification is adopted. As shown in the following figure, the self-tapping screw sleeve is fixed on the corresponding model screw. Use the same type of nut to fix the three as a whole. Use a wrench to screw the screw into the bottom hole and then remove the screw.
Self-tapping screw sleeve installation method 2: When the number of installations is large, a special screw sleeve installation tool can be used. The specific operation method refers to the following figure. The end of the tool in the figure is a hex head, which can be connected to a manual tap wrench or an electric or pneumatic tool.
Self-tapping screws
Self-tapping screw sleeve installation precautions
1. For different machining materials, refer to the hole size specifications for pre-drilling. When the hardness of the corresponding material is high, slightly increase the bottom hole opened in the drilling area.
2. Insert the self-tapping insert completely into the front end of the tool with the slotted end down and perpendicular to the workpiece. When loading (1 to 2 pitch), make sure to align with the bottom hole and never tilt it. When you find a tilt, do not reverse the tool and readjust it before use. When you enter 1/3 to 1/2, you can't come back again. In addition, please do not rotate the tool in the reverse direction, otherwise it will cause product failure.