Unlike ordinary mechanical threads, the threads of self-tapping screws do not need to be matched with nuts during use, and can be directly screwed into the base for connection and locking.

The letter used to describe self-tapping screws is “ST”. If the thread size is 4.2mm and the length is 13mm, its description is ST4.2*13mm.

Stainless steel self-tapping screws are divided into pan head and countersunk head. They are also the two most commonly used standards.

Self-tapping screws are used for non-metallic or soft metals, and do not need to drill and tap; self-tapping screws are pointed, so that they can “self-tapping”; ordinary screws are flat-headed and have the same thickness.

Self-tapping screws have high hardness, wide thread spacing, deep threads, and non-smooth surface.

Wood screws are the opposite. The other difference is more obvious. There is no thread in the back of wood screws.

Wood screws are thin, blunt and soft. The thread of self-tapping screws is thick, sharp and hard.

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Preventive measures

For those who use self-tapping screws, it is clear that self-tapping screws must be heat treated, which is what we often call hardening.

Because self-tapping screws or screws are used for tapping and tapping to achieve a fastening connection, it is necessary that the self-tapping screw itself should have a strong hardness to make it work.

The self-tapping screw just produced, the hardness of the self-tapping screw itself is not enough to meet customer requirements.

At this time, we need to go through the heat treatment of the screw, which is to harden the screw.

At that time, often when we were not paying attention, some self-tapping screws would bend during the hardening process, especially the occurrence of long screws.

In this case, what should we pay attention to when hardening? How can we better prevent this from happening and reduce the damage to the screws?

Heat treatment causes self-tapping screws to bend, which is often due to the stacking of heated self-tapping screws.

The area of ​​long screws is large, and the stacking of screws causes part of the area to be heated unevenly, resulting in bending.

Of course, in addition to this reason, there are also some factors. For example, the furnace temperature rises too fast, the temperature is too high during quenching, etc.

which are all factors of bending. The temperature in the heating furnace exceeds the critical point of the material too much, and it is easy to deform.

Therefore, both hardening factories and consumers should understand that the above points should be paid attention to when self-tapping screws are hardened by heat treatment to prevent defective products or damage the screws.