GB/T6171 Hexagon Nuts - High Precision Mechanical Connections
Kesle GB/T 6171 Hexagon Nuts Serve High-Precision Mechanical
Connections
Basic Information
Product Name: GB6171 Type A Class 1 Hexagonal Nut
Implementation Standard: GB/T 6171-2016 (current latest version)
Specification Range: Thread size: M1.6~M16 (Class A precision is mainly applicable to
thread diameters ≤16mm; larger diameters are generally Class B)
Structural and Precision Features
Structural Type: Type 1 hexagonal nut (standard hexagonal structure, no special
grooves or through-hole designs). Key dimensions such as across
flats width (s) and thickness (m) are strictly implemented in
accordance with standards.
Precision Grade: Class A represents high precision, with a thread tolerance of 6H.
Dimensional tolerances for across flats width, thickness, etc., are
smaller (superior to Class B), and the surface roughness is lower
(usually Ra≤3.2μm), making it suitable for precision connection
scenarios.
Materials and Performance
Material Selection: Materials are matched according to performance grades:
- Carbon steel: such as 35# steel, 45# steel (suitable for performance grades 6,
8, etc.), subjected to quenched and tempered heat treatment
- Stainless steel: e.g., 304 (A2-70), 316 (A4-70), suitable for corrosion-resistant
scenarios
- Copper/aluminum: e.g., brass (CU2), aluminum alloy (AL4), suitable for conductive
and lightweight applications
Mechanical Performance: Meets the requirements of specified performance grades (6, 8, 10,
A2-70, etc.):
- Yield load: Threads show no plastic deformation under specified loads
- Hardness: For example, the hardness of Grade 8 is 22~32HRC; the tensile
strength of A2-70 is ≥700MPa
- Corrosion resistance: Stainless steel/copper materials pass salt spray tests (e.g., 304
stainless steel can resist red rust for ≥48 hours)
Surface Treatment
Options based on application environment:
| Material | Treatment Options |
|---|
| Carbon steel | Zinc plating (color zinc, white zinc, salt spray resistance ≥72
hours), chrome plating (bright and wear-resistant), phosphating
(rust-proof primer), dacromet (high corrosion resistance, suitable
for outdoor use) |
| Stainless steel | Passivation treatment (enhances corrosion resistance) |
| Copper/aluminum | Natural color (for conductive scenarios) or nickel plating
(improves wear resistance) |
Application Scenarios
Due to its high Class A precision and good surface quality, it is
often used in occasions requiring strict connection precision and
reliability:
- Precision machinery and equipment (e.g., machine tools, instruments
and meters)
- Automotive parts (engines, transmission connections)
- Electronic equipment (components requiring low-tolerance
connections)
- Building steel structures (matching high-precision bolts)
Quality Control
- Dimensional inspection: Verify across flats width, thickness, and thread precision through
2D measuring instruments and thread go/no-go gauges (6H)
- Performance testing: Check hardness with hardness testers and verify load with tensile
testing machines
- Visual inspection: No cracks, burrs, or rust, and surface roughness meets Class A
requirements
GB6171 Type A nuts ensure interchangeability and reliability
through standardized production, serving as common fasteners for
high-precision threaded connections in the industrial field.
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