How to correctly choose the self-tapping screws

Update:11-02-2019
Summary:

When we choose the self-tapping screws, we will analyze […]

When we choose the self-tapping screws, we will analyze the influence of various factors on the aperture, and we can get some inspiration from the determination of the aperture size and the relative relationship between the appropriate torque and the limit torque to answer the “tightening torque”. How big is this problem. Which type of self-tapping screw is used on a part is correct, it should be a normal self-tapping screw. Self-cutting self-tapping screws, self-squeezing self-tapping screws or self-drilling self-tapping screws? In general, the main case of the application is easier to determine. E.g:

1. The screw only acts as a connection, or it has to withstand a considerable external load.

2. What materials are to be connected, steel, cast iron, aluminum, plastic, wood or other materials?

3. What is the thickness of the connector?

4. The self-tapping screws penetrate the connector or enter the blind hole connection.

5. If the penetration, the dead space is limited

6. Are drill cuttings and tapping chips harmful?

7. Is the pre-made hole drilled, dug, punched out, punched out or extruded?

8. Self-tapping screw assembly method, manual, semi-automatic or fully automatic

9. Do you need regular disassembly?

10. Is the assembly subject to vibration?

11. Whether the working environment is corrosive

12. Fastener cost and assembly cost.

Self-tapping screws of the same nominal diameter, the diameter of the self-tapping thread and the machine thread are different, so the aperture size is also different. However, most applications only need two sets of aperture sizes, and one set is used for self-squeezing with machine threads. The tapping angle of the tapping screw and the self-cutting self-squeezing screw and the ordinary self-tapping screw are usually also applicable to the self-cutting self-tapping screw, because all other known parts are the same, and the cutting torque of the self-tapping self-tapping screw is lower than that of the ordinary self-tapping screw. And "thread forming" torque for self-squeezing self-tapping screws.

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