Essential Factors in Choosing the Right Fastener Joint
1.Functional Requirements
Define the primary purpose: Connection, fixation, load transfer, sealing, or positioning?
2.Connection Method
- Removable assembly? → Use bolt-nut pairs.
- Permanent/semi-permanent? → Opt for thread-forming/tapping screws.
3.Dimensional Specifications
- Diameter (e.g., M6, M8)
- Thread Pitch (coarse/fine)
Length
Precision matching is essential for structural integrity.
4.Strength Grade (Critical Parameter!)
- Bolts: 4.8, 8.8, 10.9, 12.9
- Screws: 4.8, 8.8, A2-70, A4-80
Higher numbers = greater strength - Example: Grade 8.8 = 800 MPa tensile strength / 640 MPa yield strength.
- Risk of underspecification: Fracture failure.
- Risk of overspecification: Cost waste or component damage.
5.Operating Environment
- Outdoor humidity? Chemical exposure? High temperature? Vibration?
Dictates material and surface treatment: - Coastal applications → Stainless steel (A4/316) or hot-dip galvanizing
- Chemical plants → A4-80 stainless or specialty coatings
6.Anti-Loosing Requirements
For high-vibration environments:
- Locking nuts (nylon insert / all-metal locking)
- Spring washers
- Thread-locking adhesives
7.Compliance Standards
Adhere to international (ISO), national (GB), industry (DIN, ANSI), or corporate standards to ensure:
- Interchangeability
- Quality assurance
- Regulatory compliance
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