Introduction to GB/T 3098.9 Standard
This standard specifies the mechanical properties of prevailing torque type steel locknuts, ensuring they provide reliable locking performance against vibration and loosening in mechanical assemblies. It covers grades 04, 05, 5, 6, 8, and 10, with detailed test clamping forces and prevailing torques for thread sizes from M5 to M39. These parameters are essential for engineers to select appropriate locknuts, maintaining joint integrity in applications like automotive, aerospace, and heavy machinery.
The standard references proof loads from GB/T 3098.1 and GB/T 3098.2, defining test conditions to evaluate total friction coefficient (μ_tot) and torque retention after multiple cycles. Proper application prevents over-tightening or failure, enhancing safety and longevity of fastened connections.
Grade 04 Locknuts Clamping Force and Prevailing Torque
For grade 04 locknuts (5 mm ≤ D ≤ 39 mm), the test clamping force F_80 is 80% of the proof load per GB/T 3098.2. Upper limit F_75 is 75% and lower limit F_65 is 65% of proof load. First on-torque T_FV max applies to all-metal locknuts; for non-metallic inserts, it is 50% of listed values. Fifth off-torque T_Fd min ensures sustained locking after reuse.
- Use SPC for evaluation, independent of statistical methods.
- Guide: Select based on assembly torque to avoid thread damage.
- Professional tip: Verify with compatible bolts for optimal performance.
Soalan Lazim
How is the test clamping force calculated for grade 04 locknuts?
It is 80% of the proof load specified in GB/T 3098.2 for diameters 5 mm to 39 mm. This value ensures the locknut can achieve required preload without yielding, essential for low-load applications.
What adjustment is made for non-metallic insert locknuts?
The maximum first on-torque is 50% of the value for all-metal types to prevent damage to the insert during installation. Always check product specifications for compatibility with mating bolts.
Why are upper and lower clamping force limits defined?
They evaluate the total friction coefficient (μ_tot) between 65% and 75% of proof load, helping assess assembly consistency and preventing over or under-tightening in production lines.
How does grade 5 differ in clamping force for larger diameters?
For D > 24 mm, it uses 80% of grade 4.8 bolt proof load from GB/T 3098.1, ensuring safe performance in oversized applications where higher grades may be excessive.
What is the significance of the 5th off-torque?
It verifies torque retention after multiple cycles, indicating the locknut’s ability to maintain locking in reusable assemblies, crucial for maintenance-heavy equipment.
How to choose between grade 8 and 10 for high-vibration environments?
Grade 10 offers higher clamping forces for severe loads; compare proof loads and torques with application requirements to balance strength and cost effectively.
