Auto Lok Nuts MJ Threaded

The MJ thread form is the aerospace metric standard, featuring a larger root radius to support better fatigue behavior and commonly specified with tighter internal tolerances (for example 4H6H / 4H5H). Choose ALNsbMJ when the drawing explicitly requires an MJ internal thread.

• Reusable all-metal prevailing-torque locking (no nylon element)
• Suitable for drawings that specify MJ internal threads
• Reduced prevailing torque to support smoother assembly and consistent re-installation

Do you have MJ thread Auto-Lok nuts?

Yes. Auto-Lok offers MJ-thread prevailing-torque nuts for aerospace applications, including the EN 3152-compliant ALNsbMJ (A286) range and HSRF MJ options available from stock in sizes MJ2 through MJ10. MJ is the aerospace metric standard thread form, designed with a larger root radius for improved fatigue behavior and typically specified with tighter internal tolerances such as 4H6H / 4H5H.

Choose MJ instead of standard metric M when the engineering drawing/specification explicitly requires an MJ thread form, or when thread-root fatigue performance is a primary concern (typical in aerospace). Always match MJ internal threads with MJ external threads.

Note: Prevailing torque is not the same as tightening torque. Apply the installation torque specified for your joint (based on fastener size/grade and lubrication), and confirm that the nut’s prevailing-torque range meets your requirement (e.g., per ISO 2320 limits and test method).

Material, surface finish, classification, thread, tolerances, qualification, and acceptance criteria are defined by:

DIN EN 3152:2005 (DE) – Aerospace, Self-locking nuts with MJ thread, manufactured from high heat-resistant steel FE-PA2601 (A286), silver-plated or uncoated — Strength class 1100 MPa (room temperature) / 425 °C — Technical delivery conditions (German and English; based on EN 3152:2004).

This standard specifies the technical requirements, qualification procedures, and required quality-assurance documentation for self-locking nuts made from FE-PA2601 / A286, with a 1100 MPa strength class at room temperature and a maximum test temperature of 425 °C.

Auto-Lok HSRF with aerospace MJ internal thread profile.

Auto-Lok Nuts Titanium ALNhsrfMj

Auto-Lok supplies titanium MJ-thread prevailing-torque nuts for demanding aerospace use. Titanium combines a high strength-to-weight ratio with strong corrosion resistance, while the MJ thread form uses a larger root radius and defined aerospace tolerance classes to support improved fatigue performance.

• Material: aerospace-grade titanium (lightweight, corrosion-resistant)
• Thread form: MJ (metric aerospace), typically 4H6H / 4H5H internal classes
• Locking system: reusable all-metal prevailing torque (no nylon insert)

When to choose Titanium MJ nuts

Use Titanium MJ nuts when your drawing or standard specifies the MJ thread form, or when thread-root fatigue performance is a key requirement. Always match MJ internal threads with MJ external threads.  

For installation, apply the tightening torque defined for the joint (based on fastener size, property class, and lubrication) and confirm the nut’s prevailing-torque range meets your specification.

These ALNmj nuts are intended for MJ3 to MJ12 fine-pitch threads and are used on components such as engine accessories, actuators, high-temperature brackets and other aerospace hardware where conventional metric lock nuts are not suitable.

The all-metal prevailing torque design maintains clamp load under vibration, thermal cycling and load reversals, while still allowing disassembly for inspection and maintenance.

• Material grade: Stainless steel A286
• Finish: Passivated for improved corrosion resistance
• Performance class: 1100 MPa
• Thread types: MJ3 × 0,5 up to MJ12 × 1,25 (4H/5H or 4H/6H)

Need support selecting the right ALNmj nut or MJ thread tolerance?
Contact our engineering team for help with sizing, materials and aerospace standards.