The technological process of the self-tapping screw is generally wire annealing wire rod coil breaking cold heading rubbing wire heat treatment surface treatment. The details are subject to the manufacturer.
1、 Basic information
Standard: din7982, corresponding to international standard iso7050. Din7982 and iso7050 are slightly different in the thickness and diameter of the head.
Groove type: H: cross groove; Z: millet groove
Tail: C tail cone end f tail flat end, as shown in the following figure:
Head: sink angle is different according to the standard. Din7982 is 80 ° and iso7050 is 90 ° and each upper limit is + 2 °
Specification: the marking method of the self-tapping screw is different from that of machine screw. The common thread nominal diameter range is st2.2-st6.3mm, and the length L is 4.5-160mm.
Tolerance: refer to ISO 4759-1
Material: carbon steel
Carbon steel coating: blue white zinc, nickel plating
Before installation, the countersunk head tapping screw needs to be countersunk so that the countersunk head can sink into the preset hole. However, the difference of DK head diameter in din7982 and iso7050 standards should be fully considered in the design of counterbore.
2： Mechanical properties:
Failure torque: in general, failure torque can be tested if necessary. This can verify whether the self tapping screw has the proper torsional strength, and the corresponding test can refer to the corresponding standards.
About hardness:
Surface hardness ≥ 450hv0.3, core hardness: ≤ st3.9:270-370hv5; ≥ st4.2:270-370hv10
The hardness grade of stainless steel self tapping screw is 20h according to iso3506-4
Depth of carburized layer:
Carbon steel self tapping screw generally needs carburizing and quenching in the production process. The heat treatment process can increase the surface hardness of the workpiece and improve its wear resistance.
Screw in performance:
When the self tapping screw is screwed in, the matching internal thread can be drilled out without damage to the thread.