Nuts are one of the most widely used fasteners in industrial manufacturing and decoration assembly. They are normally matched with bolts and screws to lock, fix and connect mechanical components. A variety of nut types and complete specifications are available on the market. Among them, stainless steel nuts are widely adopted due to excellent corrosion resistance, rust-proof performance and strong adaptability to diverse working conditions. During product selection, it is necessary to accurately distinguish specification models, thread types, material grades and precision standards, so as to avoid assembly failure caused by incorrect selection.
1. Common Nut Types and National Standards
Nuts are classified by external structures into hexagon nuts, square nuts, wing nuts, ring nuts, knurled thin nuts and other types. Each category corresponds to independent national standards that clearly define dimensional specifications, machining accuracy and technical requirements. Common standards are listed as follows:
1. Grade C Square Nuts: GB/T 39-1988
2. Grade C Type 1 Hexagon Nuts: GB/T 41-2016
3. Thick Hexagon Nuts: GB/T 56-1988
4. Wing Nuts: GB/T 62-1988
5. Ring Nuts: GB/T 63-1988
6. Knurled Thin Nuts: GB/T 807-1988
2. Nut Specifications and Thread Classification
According to thread profiles, nuts are divided into coarse thread and fine thread types, which share the same nominal specification system. Common metric sizes include M3, M4, M5, M6, M8, M10 and other regular specifications.
Based on measurement systems, nuts are categorized into metric (national standard), imperial and American standard systems. Metric national standard nuts are prioritized for domestic production and conventional assembly, while imperial and American nuts apply to imported equipment and mechanical assemblies. Different systems have non-interchangeable thread pitches and outer diameters and cannot be mixed in use.
3. Common Nut Materials and Strength Grades
The mainstream nut materials are carbon steel and stainless steel. Copper and aluminum alloy nuts are only used for special lightweight or conductive applications and are rarely adopted in general assembly scenarios.
1. Carbon Steel Nuts: Featuring low cost and stable strength, carbon steel nuts are mainly classified into Grade 4.8 ordinary nuts and Grade 8 high-strength nuts, suitable for most general machinery, steel structure and decoration assembly scenarios.
2. Stainless Steel Nuts: SUS304 stainless steel nuts are the mainstream product on the market with outstanding corrosion resistance, toughness and stability, ideal for humid, outdoor and corrosive environments. SUS201 stainless steel nuts are seldom produced and applied due to unstable hardness during wire processing, easy crack formation during forming and poor rust resistance, which are not recommended for general use.
4. Precision Classification and Application Scenarios of Hexagon Nuts
As the most widely used fastener type, hexagon nuts cooperate with bolts and screws to fasten components. They are divided into multiple types according to machining precision and structural thickness to meet different assembly requirements:
1. Grade C Hexagon Nuts: Low machining precision and relatively large surface roughness, applicable to ordinary equipment, steel structures and building assemblies with low precision and simple surface treatment requirements.
2. Grade A & B Precision Hexagon Nuts: High surface finish and strict dimensional tolerance, suitable for precision machinery, high-end equipment and precision tooling requiring high assembly accuracy.
3. Type 2 Thickened Hexagon Nuts: With increased thickness and higher load-bearing capacity, they are widely used in frequently disassembled and repeatedly fastened connection positions with excellent fatigue resistance.
4. Thin Hexagon Nuts: Featuring smaller thickness, they are specially applied to scenarios with limited assembly space and insufficient installation thickness for auxiliary locking and anti-loosening positioning.
5. Selection and Application Summary
Complete ranges of nut specifications, materials and structural types fully meet the diverse demands of industrial production, equipment assembly and decoration engineering. In practical selection, specifications and materials shall be determined according to service environment, assembly precision, load-bearing requirements and anti-corrosion standards. Proper daily maintenance of fasteners can effectively delay aging, corrosion and fatigue loss, extend service life, and avoid assembly failures and potential safety hazards caused by mismatched materials, incorrect specifications and improper maintenance.
