1、 Drilling is preferred for steel structure (engineering structure) parts. Punching is allowed when it is proved that the quality, thickness and aperture of some materials will not cause brittleness after punching. Drilling is carried out on the drilling machine and other machinery, which can drill steel structure components (parts) of any thickness. The advantage of drilling is that the hole wall damage of bolt (composition: head and screw) is small and the quality is good.
2、 In the processing and manufacturing of steel structure (engineering structure), punching is generally only used to punch non-circular holes and thin plate holes (property: Gem academic language). The aperture of punching must be greater than the thickness of the plate. Punching is allowed for all common steel structures with thickness less than 5 mm, and punching is allowed for secondary structure thickness less than 12 mm. No subsequent welding (groove) is allowed on the punching hole, unless it is proved that the material still retains considerable toughness after punching. In general, when the hole needs to be punched again, the punching must be 3 mm smaller than the specified diameter.
3、 When the machining accuracy of steel structure (engineering structure) is high, there are many layers of plates and many holes of the same kind, the method of drilling mould hole or pre drilling small hole diameter (aperture) and expanding hole during assembly can be adopted. When the plate stack is less than 5 layers, the diameter of the pre drilled hole is less than grade 1 (3 mm) of the nominal diameter, and when the stack is more than 5 layers, it is less than grade 2 (6 mm) of the nominal diameter.
4、 Flat drill bit is commonly used in drilling, and pointed bit is used for drilling hole. When the stack is thick, the diameter is large, or the material strength is high, a group drill bit which can reduce the cutting force should be used to facilitate chip removal and reduce the wear of the bit (a basic type of component failure).
5、 The long hole can be processed by oxygen cutting at both ends of the hole, but the length of the hole must be more than 2 times of the diameter of the hole.
6、 When drilling steel structure (engineering structure) parts, high strength bolt hole should be drilled.