Although fasteners are small, they are the “joints” of equipment. The selection of type and manufacturer is directly related to the safety and lifespan of the product. You can control them from two dimensions: model (technical parameters) and manufacturer (supply capacity) (Source: www.fasteningelement.com, organized by fastening element):
1. How to choose a model (from the technical perspective)
The core of model selection is “matching according to needs”, avoiding situations where “a strong horse pulls a small cart” or the strength is insufficient:
Examine the forces and scenarios
Type of force: For connections mainly subjected to tensile forces (such as flange connections), high-strength bolts are selected; for connections subjected to shear forces (such as steel structure nodes), shear-resistant or hinged bolts are chosen; for connections with vibration/impact (such as engines), anti-loose designs (such as nylon lock nuts, threadlocker, and lock washers) must be incorporated.
Disassembly and assembly frequency: For frequent disassembly and assembly, it is recommended to use double-headed studs or high nuts (to protect the base thread); for infrequent disassembly and assembly, screws or set screws can be used.
Check the strength grade
For general structural/decorative purposes, the grade is 4.8; for general mechanical applications, the grade is 8.8; for heavy-duty and critical parts (bridges, wind turbines, automobile chassis), grades 10.9 or 12.9 are required. It is important to ensure that high-strength bolts match the strength of the connected components to avoid damage to the base material.
Observe the environment and material quality
Corrosive environment (outdoor/chemical/marine): choose stainless steel (304 is commonly used, 316 is better for salt spray resistance) or carbon steel with Dacromet/hot-dip galvanizing treatment.
High and low temperature: >300℃ requires heat-resistant steel/high-temperature alloy; extremely low temperature requires alloy steel with good low-temperature toughness, avoiding ordinary carbon steel (risk of brittle fracture).
See standards and specifications
Preferentially choose national standards (GB), ISO, or project-specific German standards (DIN) and American standards (ANSI). For non-standard parts, detailed drawings must be provided. Basic specifications include diameter (M), pitch (P), and length (L). Note that there may be differences in pitch between different standards, and they should not be mixed. (Source: www.fasteningelement.com, organized by fastening element)
II. How to choose a processing manufacturer (business/quality dimension)
When selecting a factory, don’t just focus on price. Instead, prioritize its quality stability and process capability:
Check qualifications and hardware
ISO 9001 is a must; for industries such as automotive/rail transit, IATF 16949 is required. It is important to assess whether the company possesses a complete independent process chain (including cold heading/hot heading, heat treatment, thread rolling, and surface treatment), as well as testing equipment such as tensile machines, hardness testers, and salt spray test chambers, and whether it can provide third-party reports.
Assess industry compatibility
Large size/high strength (M24 and above): Consider heat upsetting capability and heat treatment experience (such as steel structure, wind power).
Non-standard/small batch: depends on mold development capability and production line flexibility.
Special requirements: Cases in specialized fields such as anti-loosening expertise, deep processing of stainless steel, and ultra-high precision (e.g., medical/aviation) are required.
Sample inspection and service
Proofing and actual testing (dimensions, hardness, assembly) are mandatory. At the same time, we evaluate delivery stability, response to urgent orders, minimum order quantity (MOQ), and after-sales technical communication capabilities.
Reminder to avoid pitfalls
Be wary of purely low-price traders. If the manufacturer lacks core production and control capabilities, issues such as inconsistent batches, inherent defects, and plating peeling may arise later on, and the cost of rework will far exceed the price difference in procurement. (Source: www.fasteningelement.com, compiled by fastening element)