GB/T 6172.2-2016 Hex Thin Lock Nuts Non-Metallic Insert
1. Introduction
Hexagon thin lock nuts with non-metallic inserts are essential fasteners in mechanical engineering, providing reliable locking mechanisms to prevent loosening under vibration. The GB/T 6172.2-2016 standard specifies the dimensions, technical requirements, and markings for prevailing torque type hexagon thin nuts with non-metallic inserts. This standard is crucial for ensuring consistency and quality in manufacturing and application across industries such as automotive, aerospace, and machinery.
These nuts are designed for use in assemblies where space is limited, offering a thin profile while maintaining locking performance through a non-metallic insert, typically nylon, which provides prevailing torque. The standard covers sizes from M3 to M36, ensuring compatibility with various bolt threads.
2. GB/T 6172.2-2016 Standard Overview
Released in 2016, GB/T 6172.2 supersedes earlier versions and aligns with international standards like ISO 10511 for prevailing torque hexagon thin nuts. It applies to nuts made from steel with non-metallic inserts, focusing on type dimensions and performance.
The standard’s scope includes mechanical properties, tolerances, and surface treatments, making it applicable for general-purpose fastening in engineering contexts.
3. Dimensions and Specifications
The standard defines key dimensions for hexagon thin lock nuts, ensuring precise fit and function. All dimensions are in millimeters (mm). Below is a table summarizing the specifications for thread sizes from M3 to M36.
| Thread Size D | M3 | M4 | M5 | M6 | M8 | M10 | M12 | (M14) | M16 | M20 | M24 | M30 | M36 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| P (hauteur) | 0.5 | 0.7 | 0.8 | 1 | 1.25 | 1.5 | 1.75 | 2 | 2 | 2.5 | 3 | 3.5 | 4 |
| dun max | 3.45 | 4.6 | 5.75 | 6.75 | 8.75 | 10.8 | 13 | 15.1 | 17.3 | 21.6 | 25.9 | 32.4 | 38.9 |
| dun min | 3 | 4 | 5 | 6 | 8 | 10 | 12 | 14 | 16 | 20 | 24 | 30 | 36 |
| dw min | 4.56 | 5.9 | 6.9 | 8.9 | 11.6 | 14.6 | 16.6 | 19.6 | 22.5 | 27.7 | 33.2 | 42.8 | 51.1 |
| e min | 6.01 | 7.66 | 8.79 | 11.05 | 14.38 | 17.77 | 20.03 | 23.35 | 26.75 | 32.95 | 39.55 | 50.85 | 60.79 |
| h max | 3.9 | 5 | 5 | 6 | 6.76 | 8.56 | 10.23 | 11.32 | 12.42 | 14.9 | 17.8 | 22.2 | 25.5 |
| h min | 3.42 | 4.52 | 4.52 | 5.52 | 6.18 | 7.98 | 9.53 | 10.22 | 11.32 | 13.1 | 16 | 20.1 | 23.4 |
| m min | 1.55 | 1.95 | 2.45 | 2.9 | 3.7 | 4.7 | 5.7 | 6.42 | 7.42 | 9.1 | 10.9 | 13.9 | 16.9 |
| mw min | 1.24 | 1.56 | 1.96 | 2.32 | 2.96 | 3.76 | 4.56 | 5.14 | 5.94 | 7.28 | 8.72 | 11.12 | 13.52 |
| s max | 5.5 | 7 | 8 | 10 | 13 | 16 | 18 | 21 | 24 | 30 | 36 | 46 | 55 |
| s min | 5.32 | 6.78 | 7.78 | 9.78 | 12.73 | 15.73 | 17.73 | 20.67 | 23.67 | 29.16 | 35 | 45 | 53.8 |
| Weight per 1000 pcs (steel) ≈ kg | 0.335 | 0.694 | 0.94 | 1.85 | 3.61 | 7.01 | 10.18 | 15.08 | 22.03 | 38.98 | 68.12 | 145.2 | 243.8 |
4. Technical Requirements
The nut body is made from steel, with the insert recommended as nylon 66. General technical conditions follow GB/T 16938. Thread tolerance is 6H per GB/T 193 and GB/T 9145. Mechanical performance grades are 04 or 05 (QT) for M5 to M36, with smaller sizes per agreement, referencing GB/T 3098.2 and GB/T 3098.9.
Tolerances: Product grade A for D ≤ 16 mm, B for D > 16 mm, per GB/T 3103.1. Surface treatments include untreated, electroplating per GB/T 5267.1, or non-electrolytic zinc flake per GB/T 5267.2. Surface defects follow GB/T 5779.2, and acceptance/packaging per GB/T 90.1 and GB/T 90.2.
5. Key Requirements in GB/T 6172.2-2016
The standard emphasizes prevailing torque for locking, ensuring nuts resist vibration. Materials must meet specified grades for durability. Testing includes torque verification to confirm locking performance.
6. Applications and Industry Impact
These nuts are used in automotive assemblies, machinery, and electronics for secure fastening in compact spaces. The standard enhances quality control, reducing failure risks in critical applications.
7. Frequently Asked Questions (FAQ)
- What materials are recommended for the non-metallic insert?
- The standard recommends nylon 66 for its durability and locking properties.
- What is the thread tolerance specified?
- Thread tolerance is 6H, ensuring compatibility with standard bolts.
- How does this standard differ from GB/T 6172.1?
- GB/T 6172.2 focuses on thin nuts with non-metallic inserts, while 6172.1 covers all-metal types.
- Quels traitements de surface sont autorisés ?
- Untreated, electroplated per GB/T 5267.1, or zinc flake coated per GB/T 5267.2, with others by agreement.
- For what sizes is product grade A applied?
- Product grade A for diameters ≤ 16 mm, and B for > 16 mm.
- How is the prevailing torque tested?
- Per mechanical performance standards like GB/T 3098.9, ensuring consistent locking force.
