1、 Drilling is preferred for steel structure (engineering structure) parts. When it is proved that the quality, thickness and aperture of some materials will not cause brittleness after punching, punching is allowed. Drilling is carried out on the drilling machine and other machinery, which can drill steel structural members (parts) of any thickness. The advantage of drilling is that the wall damage of bolt (composed of head and screw) hole is less and the quality is better.
2、 In the processing and manufacturing of steel structure (engineering structure), punching is generally only used for punching non-circular holes and thin plate (property: Gem academic language). The aperture of punching must be greater than the plate thickness. Punching is allowed for all ordinary steel structures with thickness less than 5 mm, and punching is allowed for secondary structures with thickness less than 12 mm. On the punching hole, no subsequent welding (groove shape) is allowed unless it is proved that the material retains considerable toughness after punching. In general, when the hole needs to be punched is reamed again, the diameter of the punch must be 3 mm smaller than the specified diameter.
3、 When the steel structure (engineering structure) processing requires high precision (degree), more laminates and more holes of the same kind, the method of drilling mold holes or pre drilling smaller diameter (aperture) and reaming during assembly can be adopted. When the laminate stack is less than 5 layers, the diameter of pre drilled hole is less than 3 mm of the nominal diameter, and when the laminate stack is more than 5 layers, it is less than grade II of the nominal diameter (6 mm).
4、 Flat bit is often used in drilling, and pointed bit is used in drilling. When the stack is thick, the diameter is large, or the strength of the material is high, the group drill bits which can reduce the cutting force should be used to facilitate chip removal and reduce the wear of the drill bits (a basic type of component failure).
5、 Long holes can be drilled at both ends and cut with oxygen in the middle, but the length of the hole must be more than twice the diameter of the hole.