There is no national standard for combination screws, but under normal circumstances, combination screws will be discontinued in accordance with GB/T 5779.1-2000 "Fasteners, Bolts, and Studs". Hardware furniture screws

GB/T1-2000 "Fasteners - Bolts, Screws, and Studs" specifies the technical requirements for the size, specifications, data, mechanical properties, and surface treatment of composite bolts to ensure their reliability and safety during use.

The size calculation method for combination screws is as follows: 1

The length L of the bolt should meet the design requirements or be calculated using the following formula: L=L '+△ L.

△ L=m+2s+ip.

According to formula (4.2.12-1), when L ≤ 100mm, the length of the bolt can be calculated using the rule of 5mm as a specification, and its single digits can be rounded to the nearest 2 or 3 or 7 or 8 according to the standard; When L>100mm, the rule of using 10mm as a specification for bolt length can be followed.

There are two types of hardness specification requirements for combination screws, one is the ordinary specification, with a level of 4.8. Made of screw 1010A. No hard materials need to be added during manufacturing. Additionally, the customer requested a screw separation hardness level of 8.8. Our company usually uses 1018 or 10B21 screw thread to manufacture combination screws. Use 8.8 grade combination screws. Hardware furniture screws

Commonly used iron screws, if higher quality requirements are required, are generally manufactured using 1018 or all 10B21 consumables. After hardening treatment, the threaded wire can reach grade 8.8. Hardware furniture screws