How to select suitable fasteners

I Define usage scenarios and core requirements
Different scenarios have very different performance requirements, and core indicators shall be prioritized:
Building steel structure/bridge works: in high load-bearing scenes, steel structure bolts with high strength grade (8.8 and above) shall be preferred, and corrosion prevention shall meet outdoor requirements.
Outdoor photovoltaic/wind power: anti-corrosion fasteners subject to hot galvanizing and Dacromet treatment must be selected, and the salt spray test shall reach at least 1000 hours.
Engineering machinery/vibration equipment: 304 stainless steel materials are preferred, matched with professional locking structures (such as lock nuts and lock washers) to avoid vibration and looseness.
Interior furniture/general machinery: ordinary carbon steel can meet the demand and the cost is lower.
II Material selection according to environment
Materials are directly matched according to the service environment (determining the service life).
1.Humidity/corrosion Outdoor
Select 304/316 stainless steel, long-term corrosion resistant, or hot-dip galvanized carbon steel, with corrosion protection life 3-5 times of ordinary carbon steel;
2.Heavy-loaded structure
Select 45 # steel and 40Cr alloy steel, with higher strength and large load impact;
3.High and low temperature working conditions
Heat-resistant alloy material is selected to ensure stable strength under high temperature; Low-temperature steel and titanium alloy (anti-brittle fracture) shall be selected for low temperature; Chemical corrosion: 316 stainless steel, duplex steel, coating protection.
III Confirm strength and specification parameters
Exact matching can be achieved by reading the specification identifications. Check the core parameters:
strength grade
1.Strength grade: the common grades are 4.8, 8.8, 10.9 and 12.9. The higher the number is, the higher the strength is, and the higher the overload is;
Grade 4.8: ordinary, light load, indoor dry.
Class 8.8: general machinery, steel structure, most commonly used.
Level 10.9: heavy load, dynamic load, automobile/engineering machinery.
2.Specification identification
Specify load and stress type (determine specification and strength), axial tension/pressure: select common bolt, calculate diameter according to tension, commonly used (M6/M8/M10...); Transverse shear force/impact: preferentially reamed bolt (shear resistance against the rod) or common bolt+anti-loose (friction force); Vibration/alternating load: improve the strength level and use fine teeth+reliable locking; Positioning/light load: tighten the set screw and self-tapping screw.
Specification identification: e.g. M8 × 1.25 × 50, corresponding meaning: M=metric system, diameter of 8mm, pitch of 1.25mm, length of 50mm, check according to assembly size;
3.Thread standard
Thread standard: metric system (GB standard) is preferred for domestic projects, and British system (UNC/UNF) is selected for export or import equipment.
Coarse teeth (standard): generally connected, frequently disassembled and well tensioned;
Fine teeth: thin wall, vibration, precision adjustment and self-locking; Higher cost;
Pipe thread: only used for sealing (water pipe/air pipe/oil pipe), and cannot be replaced by ordinary thread.
Locking (according to vibration intensity)
Slight vibration: spring washer, nylon locknut.
Medium vibration: double nut (standard+thin).
Strong vibration/impact: wedge washer, thread locker (permanent), cotter pin+castle nut.
IV Select reliable suppliers
Preference shall be given to suppliers meeting these three conditions to reduce procurement risks:
Own the whole production line and the source manufacturer with perfect quality control system, with stronger product stability.
Provide a third-party inspection report to confirm that the salt spray test, strength and other indicators meet the standards.
For procurement of various types of fasteners, the one-stop supplier shall be preferred to reduce communication and docking costs.