Introduction
GB/T 3098.9-2020 specifies the mechanical properties of torque-controlled steel lock nuts, which are designed to provide reliable locking performance through prevailing torque. This standard covers property classes including 04, 05, 5, 6, 8, and 10 for nuts with thread diameters from M5 to M39. It defines requirements for test clamping forces and prevailing torques during installation and removal cycles, ensuring consistent performance in fastening applications. These specifications are crucial for industries such as automotive, aerospace, and machinery where vibration resistance is essential.
The standard distinguishes between all-metal lock nuts and those with non-metallic inserts, with adjusted torque values for the latter. Clamping forces are derived from proof loads specified in related standards like GB/T 3098.2 for nuts and GB/T 3098.1 for bolts.
Test Clamping Forces and Prevailing Torques for Property Class 04
For property class 04 lock nuts with diameters from 5 mm to 39 mm, the test clamping force (F80) equals 80% of the proof load as per GB/T 3098.2. Upper limit (F75) is 75% of proof load, lower limit (F65) is 65% of proof load.
| Thread Specification | Values | ||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| M5 to M39X3 | |||||||||||||||||||||||||||||||||
| Test Clamping Force F80 / N | |||||||||||||||||||||||||||||||||
| Upper Limit F75 / N | Clamping Force for Evaluating Total Friction Coefficient (μtot) | Lower Limit F65 / N | Prevailing Torque / (N·m) | 1st On Max TFV,max | 1st Off Min TFd,min | 5th Off Min TFd,min | |||||||||||||||||||||||||||
| M5 | 4320 | 4050 | 3510 | 1.6 | 0.29 | 0.2 | |||||||||||||||||||||||||||
Notes: 1st on prevailing torque applies only to all-metal lock nuts; for non-metallic insert types, max is 50% of values. Evaluation using SPC is independent of statistics.
FAQ
- What is the difference between all-metal and non-metallic insert lock nuts in this standard?
- All-metal lock nuts use the full specified 1st on prevailing torque values, while non-metallic insert types are limited to 50% of those maximum values to account for insert material properties.
- How are clamping forces determined for property class 5 nuts?
- For property class 5, clamping force F80 is 80% of the proof load for 5.8 grade bolts per GB/T 3098.1; for diameters >24 mm, it uses 4.8 grade bolt proof loads.
- Why are there upper and lower limits for clamping forces?
- These limits (75% and 65% of proof load) ensure consistent friction coefficient evaluation, accounting for variations in manufacturing and material.
- What does the 5th off prevailing torque represent?
- It indicates the minimum torque required after five installation/removal cycles, verifying the nut’s locking performance durability under repeated use.
- How does GB/T 3098.9-2020 relate to other fastener standards?
- It references GB/T 3098.1 for bolt proof loads and GB/T 3098.2 for nut proof loads, ensuring compatibility in bolted joints.
