Lock Nuts (Self-Locking Nuts) for Anti-Loosening Performance
A nut that simply “fits” a bolt is not enough in real machines. Under vibration, thermal cycling, or repeated micro-slip, a conventional nut can lose clamp force and back off, even when the original tightening torque was correct. Lock nuts—also called self-locking nuts or prevailing torque nuts—are engineered specifically to resist rotation by creating controlled friction or mechanical interference in the thread system.
In practice, the anti-loosening function matters most where maintenance access is limited and failure cost is high: automotive brackets, solar racking, railway equipment, pumps and gearboxes, and general machine hardware. The key is selecting the correct locking mechanism: nylon insert (Nyloc / nylon insert lock nut) for general vibration environments, all-metal lock nuts for elevated temperature or chemical exposure where nylon would creep or soften, and serrated flange lock nuts (whiz nuts) where surface bite and parts-count reduction are needed. We supply lock nuts in bulk with standard compliance and material options aligned to B2B procurement and engineering verification.
- Resist loosening under vibration
- Offer nyloc and all-metal types
- Cover DIN 985 / DIN 980
- Provide serrated flange options
- Support A2/A4 corrosion grades
- Enable bulk OEM traceability packs
Technical Specifications
Product Name
Lock Nuts / Self-locking Nuts / Prevailing Torque Nuts / Torque Lock Nuts / Anti-vibration Nuts
Standards
DIN 985 (nylon insert, standard), DIN 982 (nylon insert, heavy pattern), DIN 980 / ISO 7042 (all-metal prevailing torque), ISO 7040 (non-metal insert hex lock nuts), DIN 6923 (serrated flange lock nuts), IFI 100/107 (inch lock nut programmes, on request)
Material
Carbon steel, Alloy steel; Stainless steel A2 (304) / A4 (316); special materials per project (e.g., brass)
Grades / Classes
Metric programmes: Class 8 / Class 10 / Class 12 (as specified); Stainless strength classes A2-70 / A4-70 / A4-80; ASTM grades (e.g., A194 2H) available for specific industrial programmes
Thread
Metric coarse / fine; UNC / UNF; right-hand standard
Diameter Range
Metric: common M3–M24 (larger by request); Inch sizes per IFI programmes on request
Surface Finish
Plain, Zinc Plated (blue/white/yellow), Zinc-Nickel, HDG where applicable, Black oxide, Flake coatings (Geomet/Dacromet); Passivation for stainless
Certifications
ISO 9001:2015, RoHS/REACH declarations on request; EN 10204 3.1 material certificates and lot traceability available
1: Vibration loosening despite “correct torque.”
What happens: Transverse vibration creates micro-slip at the joint interface; preload drops and the nut can rotate loose.
How lock nuts work: Lock nuts add a resisting torque (prevailing torque) through a nylon insert or all-metal deformation feature, increasing rotational resistance even as the joint experiences motion.
Pain Point 2: Temperature and chemical exposure (nylon not suitable).
Issue: Nylon inserts can soften, creep, or degrade depending on temperature and chemicals, reducing locking effectiveness.
Solution: Use all-metal lock nuts (e.g., DIN 980 / ISO 7042) when elevated temperature or aggressive environments are expected.
Pain Point 3: Lost parts and slow assembly (washer stacking).
Issue: Traditional locking solutions often add washers or multiple components, increasing assembly time and missing-part risk.
Solution: Serrated flange lock nuts (DIN 6923 / whiz nuts) integrate a flange and serrations to bite into the bearing surface and reduce parts count—best on steel surfaces where serration marking is acceptable.
Pain Point 4: Procurement mismatches (locking feature not controlled).
Issue: Two nuts can look similar but behave differently: insert height, prevailing torque range, and coating friction affect assembly and field performance.
Solution: Call out the exact standard (DIN 985 vs DIN 982 vs DIN 980), locking mechanism, and finish on the PO; for critical programmes, specify prevailing torque requirements and verification method.
Example chart for “DIN 985 lock nut dimensions” searches. Confirm exact values against the specified standard edition and tolerance class.
| Thread d | Pitch P (coarse) | Across flats s | Nut height m | Insert type |
|---|---|---|---|---|
| M4 | 0.7 | 7 | 5 | Nylon insert |
| M5 | 0.8 | 8 | 5 | Nylon insert |
| M6 | 1.0 | 10 | 6 | Nylon insert |
| M8 | 1.25 | 13 | 8 | Nylon insert |
| M10 | 1.5 | 17 | 10 | Nylon insert |
| M12 | 1.75 | 19 | 12 | Nylon insert |
Dimension notes for engineering
Ensure nut height m provides required thread engagement for the bolt’s clamp length.
For coated nuts, confirm thread fit vs coating build (avoid “tight start” that causes galling or false torque).
Achieve target preload while maintaining the lock nut’s anti-loosening function.
Torque + prevailing torque are different
Assembly torque must overcome both thread friction and the lock feature. For prevailing torque nuts, tightening torque includes the additional resisting torque from the insert/deformed threads.
For controlled builds, specify a method to account for prevailing torque (especially in automated lines).
Lubrication policy (affects locking behaviour)
Lubrication changes friction and the measured torque dramatically. If you lubricate, define it; do not mix dry and oiled assembly specifications across suppliers.
For stainless, lubrication also helps reduce galling during repeated assembly.
Re-use guidance
Nylon insert nuts lose locking effectiveness after repeated cycles; all-metal types can also relax depending on design and usage. For safety-critical joints, define re-use limits in work instructions.
Washers and bearing surfaces
For serrated flange nuts, the serrations require a suitable bearing surface (usually steel). On soft materials or coated decorative surfaces, serrations can damage the finish and reduce consistency—use a different locking strategy.
Hole clearance (ISO 273)
Lock nuts are often used in bracket assemblies with clearance holes. Follow ISO 273 clearance recommendations to avoid misalignment and “false torque” from binding during tightening.
Related Products
FAQ
What is a lock nut and how does it prevent loosening?
A lock nut is a self-locking nut designed to resist rotation under vibration by adding prevailing torque. It prevents loosening by creating controlled friction or interference in the thread system.
What is the difference between DIN 985 and DIN 982 nyloc nuts?
DIN 985 is a standard pattern nylon insert lock nut, while DIN 982 is a heavier pattern version with a taller nut body. Selection depends on required thread engagement and the joint’s mechanical demands.
When should I use an all-metal lock nut instead of a nylon insert nut?
Use an all-metal lock nut when elevated temperature, chemicals, or long-term creep risk could reduce nylon insert performance. Standards such as DIN 980 / ISO 7042 cover common all-metal prevailing torque designs.
Are serrated flange lock nuts good for anti-vibration?
Yes—serrated flange lock nuts resist loosening by biting into the bearing surface and increasing friction, but they require a suitable surface (typically steel) and can damage coatings or soft materials.
Can lock nuts be reused?
Some can, but locking performance generally decreases with each reuse cycle. Nylon insert nuts in particular lose prevailing torque after repeated assemblies; for critical joints, define reuse limits or use new nuts.