What Is a Tapping Screw?

Generally refers to pointed, coarse-toothed, harder wood screws, but also aluminum alloy, plastic. A special type of self-tapping screw for threading a metal hole is called a tap.

Self-tapping screws are a type of screw with a drill bit.

Self-tapping screws have high hardness, wide thread spacing, deep thread, and uneven surface. Wood screws are the opposite. Another difference is more obvious. There is no thread at the back of the wood screw. Wood screws are thin, blunt and soft. Self-tapping screws are thick, sharp and hard. ^[1]

Commercialization of self-tapping screws since 1914.

(Thread Forming Tapping Screws) Developed directly from iron screws.

(Thread Rolling Tapping Screws) Triangular self-tapping screws, also known as Type TT (Type Tai is still patented) are developed based on the principle of forming screw taps.

(Self Drilling Tapping Screws)-also known as Tec, in all the process of assembling self-tapping screws, the most costly preparation for pre-drilling. The use of self-tapping screws must be drilled first, and the hole diameter must be limited. No pre-drilling is required and cost savings can be achieved in some respects. This is the self-tapping screw that drills, taps, and tightens in one operation.

(Twin Lead Self Drilling Point Tapping Screws) It can be easily screwed into the dry wall when assembling, drilling a hole in the steel strip and tapping the mating female thread. The recessed bearing surface of the horn head can prevent the wallpaper or plaster surface from being damaged when screwing in. Most self-tapping screws are for commercial use. For example, when self-tapping screws are provided as combination screws (SEMS), they can provide tighter service. Special screws such as screws with thick and thin threads are designed to prevent loosening after assembly . ^[1]

Standard self-tapping screws identify characters, including symbols for thread and tail shapes. Self-tapping screws have one or two characters that represent threads to represent mechanical or wide threads (SPACED). If the identification character "B" is used, it means a wide thread screw. Those without "B" represent mechanical threads, and the characters at the end are used to distinguish self-tapping screws for thread forming, cutting, rolling or self-drilling. The mechanical thread has the same thread angle of 60 degrees and the same pitch as that of the British and American unified threads. If the screw is lost or needed after disassembly, it can be used.

The self-tapping screw is composed of the head, the stem and the end of the stem from head to tail. The composition of each self-tapping screw has four major elements: head shape, tightening method, thread type, and end type. Head shapeHead shapes vary. There are round head (semi round head), oblate head, round head flange (with pad), flat round head flange (with pad), pan head, pan head flange (with pad), countersunk head, semi-sink head, Cylindrical head, spherical cylindrical head, horn head, hexagon head, hexagon flange head, hexagon flange (with pad) and so on. Wrenching methodsVariable screwing methods. Outer wrench: hexagonal, hexagonal flange face, hexagonal flange, hexagonal flower shape, etc .; inner wrench: slotted, cross groove H (Phillips), cross groove Z (Pozidriv), cross groove F (Frearson) , Square groove (Scrulox), compound groove, internal spline, hexagonal flower (plum blossom groove), internal triangle, internal hexagon, internal 12 angle, clutch groove, six-blade groove, high torque cross groove and so on. Thread typesVarious types of threads. There are self-tapping threads (wide teeth threads), machine threads, drywall screw threads, fiberboard screw threads, and some other special threads. In addition, the threads can be divided into single-lead (single-head), double-lead (double-head), multi-lead (multi-head) and high-low tooth double-head threads. End stylesThe end styles are mainly saw ends and flat ends. However, according to the use function, grooves, grooves, cutouts or similar drill-shaped parts with cutting functions can be processed. In some standards, the same is the saw end or flat end, there are different forms. As can be seen from the introduction above, there are various changes in the shape of the head of the tapping screw, the method of tightening, the type of thread, and the type of the end of the rod. They can be combined with each other, demonstrating many different products that belong to the category of self-tapping screws. ^[1]

Self-tapping screw surface treatment: Most of the surface coating of self-tapping screws is galvanized or zinc phosphate. Cadmium plating is rarely used because of its high cost and toxicity. If the appearance is important, nickel or chromium plating can be selected. There are two doubts about appearance treatment: one is that the appearance treatment will not only increase the scale (such as the reduction of holes), and the different appearance treatment will affect the relationship between torque, tightening degree, and strength, so it is attack When entering the experiment, different rules must be applied according to zinc plating, cadmium plating or phosphate disposal. When testing the applicable drilling diameter, the screws used must be screws with the same appearance. The second is that high hardness, small-scale self-tapping screws often fail due to hydrogen embrittlement. Self-tapping screws have to be carburized in order to penetrate into the iron plate. After carburizing treatment, high hardness and high carbon content will occur, and hydrogen embrittlement will occur when electroplating or pickling treatment is performed in this case. The method proposed in the specification to eliminate hydrogen embrittlement is: a). Bake within 1 hour after plating or pickling. B). Temperature 375 ~ 425 oF (190 ~ 220 oC). At least 4 hours. Hydrogen embrittlement test: The hydrogen embrittlement test is mainly to test whether the self-tapping screw has residual hydrogen in the screw arrangement and whether it will embrittle the self-tapping screw. (The stress will only appear.) The plated or coated screws should be installed in the test iron plate and steel Pinghua Division as specified in Table 3. Oval screws use a matched steel sheet with chamfered distance. The thickness of the flat washer or distance piece installed on the bearing surface of the head should be able to fit the maximum invalid tooth length of the screw. For the half-length long screws, the shank can be supported by a long cold-rolled steel distance piece or Pinghuasi to ensure that the complete teeth can be merged and maintained in the thickness of the test plate. The screw should be tightened to 80% of the maximum breaking torque. The breaking torque is determined by tightening 5 screws to break the average value. Continue to tighten for 24 hours, then loosen the screw and then turn to the original lock Tightening torque, there should be no significant failure of the screw. ^[1]

Although there are many types of self-tapping screws, they all have the following main characteristics: (1) Generally, they are made of carburized steel (accounting for 99% of the total product). It can also be made of stainless steel or non-ferrous metals. (2) The product must be heat treated.

The definition of self-tapping screws refers to self-tapping screws that do not need to be used with nuts. The thread is self-tapping and the tail is pointed. When the triangular tooth self-extrusion screw is screwed into a hole in a plastic metal material, it forms an internal thread in the hole by extrusion to form a reliable locking screw connection. ^[1]

Generally refers to the self-tapping of the thread, so that the self-tapping effect does not need to be used with a nut. There are many types of screw heads, including external hexagon heads, pan heads, countersunk heads, and internal hexagon heads. Umbrella heads, cushioned heads, etc. The tail is usually sharp. Make it self-tapping. Self-tapping screws are also called self-tapping screws. The names are different, but the meaning is the same. All make self-tapping. The main function of self-tapping screws is that they do not need to be used with nuts. In terms of cost, a large number of them are saved. There is no need for the cost of the nut. There are many self-tapping screws, such as cross recessed pan head tapping screws, countersunk head tapping screws, pad tapping screws, umbrella head tapping screws, cut tail tapping screws, and the last post The triangular tooth self-locking screw. Triangular self-locking screws are widely used in the market. Customers also use a lot. Interested friends can look at the definition of self-locking screws, the definition and basic knowledge of triangular tooth self-locking screws. It is convenient for everyone to understand and learn. ^[1]