M4 M16 Carbon steel Flat head Philip sclotted tapping metal screws Class4.8

Product Specification

M4 M16 Carbon steel Flat head Philip sclotted tapping screws Class4.8 grade 8.8 Black

 
Product Description:
1,Ordinary self-tapping screws
The thread is ‘self-tapping thread’, also known as ‘wide thread’. The surface is mostly plated.
2,Self-cutting tapping screws
China's standard called ‘self-tapping screws shaved end’, the thread for the self-tapping thread or machine thread, cross groove is also ‘H’ type. Self-cutting tapping screws have the following types: cross recessed pan head self-cutting tapping screws, cross recessed countersunk head self-cutting tapping screws. Cross recessed raised countersunk head self-cutting tapping screws, hexagonal head self-cutting tapping screws.
3, self-extruding tapping screws (self-tapping lock screws)
Self-extruding tapping screws thread is generally machine thread, rarely use self-tapping thread. In the wrenching method, in order to ensure the use of high-speed automatic assembly wrenches, generally do not recommend the use of slotted. Self-extruding self-tapping screws have a three-pronged screw cross-section. So also known as triangular thread screws.
4, self-drilling tapping screws (self-drilling screws)
Self-drilling tapping screws thread, China, Germany and international standards for self-tapping thread. U.S. ASME and SAE standards in the BSD type self-drilling tapping screws for self-tapping thread, CSD type self-drilling tapping screws for machine thread. Self-drilling tapping screws do not recommend the use of ‘slotted’ and ‘ordinary hexagon head’.
5, metal drive screws (metal tapping screws)
Metal drive screws thread for the multi-head, and with a certain helix angle of the special thread. Only the U.S. standard metal drive screws, our country and the German standard is not.
6, wallboard tapping screws (drywall nails)
Wallboard white tapping screws for the trumpet head, cross groove (H-type), 60 ° tooth angle of the special thread, the surface of more phosphate treatment (phosphating).
7,Fibreboard nails
Cross slot for Z-type, the surface treatment is mostly plating. Fibreboard nails have the following types of several types: countersunk head, double countersunk head fibreboard nails, pan head, pan head flange (with pad) fibreboard nails, half countersunk head, half countersunk head flange (with pad) fibreboard nails.
8,Combination of self-tapping screws
Ordinary self-tapping screws, self-cutting self-tapping screws, self drilling self-tapping screws and flat washers, elastic washers (including spring washers, elastic lock washers shaped t into a combination of self-tapping screws.
9. Other self-tapping screws type
High and low teeth double lead self-tapping screws, coarse and fine teeth (different pitch) thread self-tapping screws, thread coated with sealing material (drop-resistant) self-tapping screws, a variety of composite groove self-tapping screws, other special equipment juice self-tapping screws.
Applications
Although there are many types of self-tapping screws, they all have the following common points:
(1) They are generally manufactured from carburised steel (99% of total production). They can also be manufactured from stainless steel or non-ferrous metals.
(2) The product must be heat-treated. Carbon steel self-tapping screws must be carburised, and stainless steel self-tapping screws must be solution-hardened. In order to make the self-tapping screws to achieve the mechanical properties and the use of performance required by the standard.
(3) high surface hardness, good core toughness. That is, ‘soft outside’. This is a major feature of the performance requirements of self-tapping screws. If the surface hardness is low, it is not screwed into the matrix; if the core toughness is poor, a screw on the break, can not be used. So ‘soft outside steel’ is a self-tapping screws to meet the performance, very important requirements.
(4) The surface of the product requires surface protection treatment, generally plating treatment. Some of the product surface shall be treated with phosphate (phosphating), such as wallboard tapping screws are mostly phosphated.
(5) Cold heading process is adopted. Recommended high-speed cold heading machine and high-speed thread rolling machine or high-speed planetary thread rolling machine production. High speed is emphasised here to ensure product quality. Only high-speed machine production of self-tapping screw head forming good, high thread quality.
 

What is blackening treatment
Various steel products will naturally form a film of oxides on the surface after prolonged contact with air, but this film is not very complete and dense, so it is easy to cause oxidation and corrosion of steel from the surface.

Blackening treatment is the use of a variety of chemical substances to produce a chemical reaction on the surface of the metal, so that a black oxide film is attached to the surface.

The purpose of blackening treatment is to keep the metal parts from oxidation, in order to make the metal parts completely isolated from the air, to improve the ability to prevent rust, blackening treatment can also increase the surface luster of the metal parts so that it is more beautiful, and can also reduce some of the deformation caused by the internal or external forces on the workpiece.

 
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