Product Overview
A Lock Nut is a specialized fastener designed to resist self-loosening under vibration, dynamic loads, and thermal cycling. Unlike standard nuts, it incorporates a unique locking feature that increases the friction between its threads and those of the mating bolt, maintaining clamp force and preventing unintended rotation. This critical component ensures the long-term integrity and safety of bolted assemblies in demanding environments.
Locking Mechanisms & Product Types
Lock nuts are categorized by their method of achieving a prevailing torque.
| Type | Common Name | Locking Mechanism & Features | Ideal Applications |
|---|---|---|---|
| Nylon Insert | Nylon Lock Nut (e.g., DIN 985, ISO 7040) | A non-metallic (nylon) ring deforms elastically against the bolt threads, creating a reusable friction lock. Temperature limited by nylon. | Electronics, automotive interiors, general machinery, appliances. |
| Prevailing Torque (All-Metal) | Stover Nut, Center-Lock Nut | Distorted threads or a conical top section creates an interference fit with the bolt. Reusable, higher temperature rating. | Heavy equipment, engines, high-temperature assemblies. |
| Two-Piece / Jam Nuts | – | Uses two standard nuts tightened against each other (jam nut method). A traditional, low-cost solution. | Low-speed adjustments, static/low-vibration setups. |
| Serrated Flange | Serrated Lock Nut | Integrated flange with serrated teeth that bite into the mating surface, preventing rotation. | Sheet metal, soft materials, where a washer face is needed. |
| Chemical Adhesive | Prevailing Torque Nut with Adhesive | Micro-encapsulated adhesive on threads cures after assembly. One-time use, high locking strength. | Permanent or tamper-proof assemblies. |
Key Features & Benefits
Vibration Resistance: Primary function is to prevent loosening caused by dynamic forces (Junker vibration test).
Maintained Preload: Ensures the designed clamp force is retained over the service life of the joint.
Reusability (Most Types): Many designs (nylon insert, all-metal) can be reused several times without significant loss of locking torque.
Eliminates Need for External Locking Devices: Replaces lock washers, cotter pins, or safety wire in many applications, simplifying assembly.
Temperature & Chemical Compatibility: Available in materials and designs suitable for extreme temperatures and corrosive environments.
Material Specifications & Grades
| Material Standard | Grade / Class | Typical Hardness | Characteristics |
|---|---|---|---|
| Acier au carbone | Grade 5 / 8 / 10 | HRC 22-32 (Heat Treated) | General purpose. Grade 8 and 10 are quenched & tempered for high-strength applications. |
| Stainless Steel | A2-70 / A4-80 (ISO 3506-1) | – | AISI 304 (A2) & 316 (A4). For corrosion resistance. Locking feature must be compatible with galling tendency. |
| Brass | – | – | Good corrosion resistance, non-magnetic, conductive. Often used in plumbing and electrical. |
| Aluminum | 6061-T6 | – | Lightweight, corrosion-resistant. For weight-sensitive applications like aerospace. |
Standard Series & Specifications
Our lock nuts conform to the dimensional and performance requirements of major international standards.
Nylon Insert Lock Nuts: ISO 7040 (Prevailing Torque Type), DIN 985, ASME B18.16.3M.
All-Metal Prevailing Torque Nuts: ISO 7042 (Prevailing Torque, Hexagon), DIN 6927 (Flange with non-serrated bearing surface).
High-Temperature / High-Strength Lock Nuts: MS21042 (Aerospace), proprietary grades for automotive and heavy industry.
Gamme de tailles : Metric: M3 to M36. Imperial: #4 to 1-1/2″.
Available Surface Finishes
The finish must be compatible with the locking mechanism to ensure consistent performance.
| Finish Type | Specification / Process | Note on Use with Lock Nuts |
|---|---|---|
| Zinc Plated (Trivalent/Blue/Yellow) | ASTM B633 | Most common. Trivalent chromate is RoHS compliant. Coating thickness must be controlled to not impair locking feature. |
| Hot-Dip Galvanized (HDG) | ASTM A153 | For severe outdoor exposure. The thick coating may require oversize tapping or special design consideration. |
| Zinc-Nickel Alloy Plating | – | Excellent corrosion resistance for automotive. Provides consistent locking performance. |
| Geomet® / Zinc-Flake Coating | Proprietary (e.g., Delta Protekt) | Premium Option. Superior corrosion resistance, controlled friction coefficient, ideal for critical assemblies. |
| Passivation (Stainless Steel) | ASTM A967 | Standard for stainless steel nuts to maximize corrosion resistance. |
| Black Oxide | MIL-DTL-13924 | Mild corrosion protection, reduces glare. May be waxed or oiled. |
Selection & Application Guidelines
Determine the Loosening Force: Assess the level of vibration, shock, or thermal cycling in the application.
Consider Service Environment: Temperature, exposure to chemicals, or outdoor weather will dictate material and finish.
Reusability Requirement: Specify if the joint needs to be disassembled and reassembled multiple times.
Assembly Torque: Lock nuts often have a higher installation torque due to the prevailing torque. Follow manufacturer’s recommended torque values, which include the locking feature’s contribution.
Avoid Double Stacking: Do not use two lock nuts on the same bolt, as this can compromise performance.
Manufacturing & Quality Assurance
Process Control: Lock nuts require precise control over the feature creating the prevailing torque (nylon insert placement, thread deformation, etc.).
Performance Testing: Batch testing for Prevailing Torque per ISO 2320 (for prevailing torque nuts) is critical to ensure consistent locking force.
Material Certification: Full traceability from raw material to finished product, with Mill Test Certificates (MTCs) available.
Quality System: Manufactured under a certified ISO 9001:2015 and often IATF 16949 (automotive) quality management system.
Our lock nuts are engineered and produced by Hebei Wohe Fastener Manufacturing Co. Ltd., leveraging specialized manufacturing techniques for both nylon insert and all-metal prevailing torque designs. Our facility includes dedicated production lines with in-process monitoring to ensure every nut meets the specified locking performance. We supply to industries where joint reliability is non-negotiable, including automotive, off-highway equipment, and industrial machinery.
Technical Support: We provide technical data sheets with prevailing torque specifications and installation guidelines.
Customization: Available in special sizes, proprietary locking features, and customer-specific packaging.
MOQ: Standard items start from 5,000 pieces per size/type. Custom orders are negotiable.
Lead Time: Standard specifications: 20-25 working days.
*Disclaimer: The effectiveness of a lock nut is system-dependent. Factors such as bolt grade, mating surface hardness, and correct installation torque are crucial. For safety-critical applications, physical testing of the complete joint under simulated service conditions is strongly recommended. Specifications are subject to change without notice.
