All-Metal Lock Nut (Prevailing Torque Lock Nut) | High-Temperature, Reusable Vibration Resistance
Product Overview
The All-Metal Lock Nut, also known as a Prevailing Torque Lock Nut, is a one-piece, reusable fastener engineered to prevent self-loosening under severe vibration, shock, and thermal cycling. Unlike nylon insert lock nuts, its locking feature is created by a precision deformation of the nut’s top threads (e.g., elliptical shape, deflected teeth, or non-circular top), generating a consistent, metal-to-metal interference fit with the mating bolt. This design offers superior temperature resistance, higher strength, and reliable performance in demanding mechanical and structural applications where frequent disassembly may be required.
Key Advantages
High-Temperature Capability: Can withstand temperatures exceeding 250°C (480°F), making it suitable for engines, exhaust systems, and high-heat industrial equipment where plastic inserts would fail.
Reusable Performance: The all-metal, elastic deformation allows it to be reused multiple times without significant loss of locking torque, reducing long-term maintenance costs.
Consistent Prevailing Torque: Provides a predictable and uniform resistance during both installation and removal, ensuring reliable clamp load maintenance.
High Strength: Available in property classes 8, 10, and 12, matching high-strength bolts to develop the full strength of the joint.
Full Environmental Resistance: Not susceptible to degradation from UV exposure, oils, or solvents.
Material Specifications & Property Classes
| Material Standard | Property Class (ISO) / Grade | Core Hardness | Characteristics & Typical Use |
|---|---|---|---|
| Medium Carbon Steel | Class 8 / Grade 5 | HRC 24-32 | General purpose, quenched & tempered. For automotive and general machinery. |
| Medium Carbon / Boron Steel | Class 10 / Grade 8 | HRC 28-36 | High-strength applications. Common in heavy-duty equipment and structural uses. |
| Alloy Steel | Class 12 | HRC 33-39 | Highest strength for critical, high-preload connections. |
| Stainless Steel | A2-70 / A4-80 (ISO 3506) | – | AISI 304 (A2) & 316 (A4). For corrosion-resistant applications. Anti-galling lubricant is recommended during installation. |
Locking Mechanism & Design
The nut features a controlled, elliptical distortion or non-circular top section. When threaded onto a bolt, this distortion creates radial pressure against the bolt threads, resulting in a prevailing torque that resists rotation. This elastic interaction ensures the lock remains effective through multiple installation cycles.
Product Series & Standards
Standard Hex Lock Nuts: Conform to ISO 7042 (Prevailing torque type, all-metal) and DIN 6927 (with flange).
Heavy Hex Lock Nuts: Compliant with ASME B18.16.3M.
High-Temperature Variants: Designed for specific aerospace (e.g., MS21042) or automotive standards.
Gama de tallas: Metric: M4 to M36. Imperial: #8 to 1-1/2″.
Available Surface Finishes
| Finish Type | Specification / Process | Key Benefit for Lock Nuts |
|---|---|---|
| Zinc Plated (Trivalent/Blue/Yellow) | ASTM B633 | Standard corrosion protection. Coating thickness is controlled to not impair the locking feature’s tolerances. |
| Zinc-Nickel Alloy Plating | – | Enhanced corrosion resistance for automotive and offshore applications. |
| Geomet® / Zinc-Flake Coating | Proprietary (e.g., Delta Protekt) | Premium choice. Superior corrosion resistance, excellent friction control, and consistent torque-tension performance. |
| Black Oxide/Phosphate & Oil | MIL-DTL-13924 | Mild corrosion protection, reduces glare, and aids in break-in lubrication. |
| Passivation (Stainless Steel) | ASTM A967 | Standard finish to maximize the corrosion resistance of stainless steel nuts. |
Quality Assurance
Performance Testing: Every production batch is tested for Prevailing Torque in accordance with ISO 2320 or ASME B18.16.3M to ensure consistent and specified locking force.
Material & Dimensional Checks: Full material certification and dimensional verification, including thread gauging after final forming.
Traceability: Complete traceability from raw material to finished product. Certificates of Compliance (CoC) with test results are provided.
Quality System: Manufactured under a certified ISO 9001:2015 and IATF 16949 (for automotive) quality management system.
Manufacturing Expertise at Hebei Wohe
Hebei Wohe Fastener Manufacturing Co. specializes in the precision cold-forming of high-performance fasteners like all-metal lock nuts. Our production process utilizes advanced multi-station headers and precise secondary machining to create the consistent, controlled thread deformation that defines this product’s reliability. With dedicated heat-treatment lines and a focus on process control, we ensure each nut meets its specified property class and prevailing torque requirements. We supply these critical components to the automotive, heavy machinery, and energy sectors, where joint integrity under extreme conditions is non-negotiable.
Technical & Commercial Support:
Technical Data: Prevailing torque specifications and installation torque recommendations are provided in detailed datasheets.
Customization: Available in special sizes, unique markings, and proprietary coatings.
MOQ: Standard items start from 5,000 pieces per size/grade.
Lead Time: Standard specifications: 20-25 working days.
Important Application Notes:
Do Not Double-Nut: All-metal lock nuts are designed to be used singly. Using two lock nuts together is ineffective and not recommended.
Correct Installation: Use a torque wrench for installation. The “prevailing torque” (resistance felt during running down) is part of the design and should not be mistaken for the final seating torque.
Bolt Compatibility: For optimal performance and to prevent thread damage, use with bolts of equal or higher property class and standard thread tolerances.
