Metal insert hex lock nut (Type M)

Metal Insert Hex Lock Nut (Type M) — Product Introduction

The metal insert hex lock nut (Type M) is an all-metal prevailing-torque lock nut conforming to DIN 980 M (corresponding to ISO 7042 and GB/T 6184). Its core structure features a heat-treated spring-steel metal insert embedded inside the nut face. The inner diameter of the insert is slightly smaller than the major diameter of the bolt thread; once tightened, the metal disc grips the bolt thread and generates a continuous prevailing torque, thereby preventing the nut from loosening under vibration, impact, and similar service conditions.

I. Product Features

• Metal insert structure: A fully metallic insert made of 65Mn spring steel is embedded inside the nut face. Its inner diameter is slightly smaller than the major diameter of the bolt thread, and after tightening it grips the thread to produce the locking torque.
• Excellent high-temperature resistance: With no reliance on a nylon collar, there is no risk of high-temperature melting failure. The operating temperature range reaches –70 °C to +300 °C, far superior to nylon insert lock nuts.
• Full range of sizes: Thread sizes cover M3–M36, available in both coarse and fine pitch, suiting different bolt dimensions.
• Diverse materials and grades: Carbon steel property classes cover grades 6, 8, and 10; stainless steel options include 304, 316, 316L, and 2205, corresponding to A2-70, A4-80, and similar grades.
• Optional surface treatments: Black oxide, blue-white zinc, colored zinc, black zinc, zinc-nickel alloy, hot-dip galvanizing, dacromet, and others, adapting to different corrosion-protection needs.
• Unified standard: Conforms to the DIN 980 M standard with standardized dimensions and good interchangeability, facilitating procurement and replacement.

II. Product Advantages

• Reliable locking: The metal insert grips the bolt thread to form a mechanical interference that effectively resists the reverse rotational torque generated by vibration, delivering stable anti-loosening performance.
• Outstanding vibration resistance: In high-frequency vibration scenarios, after 100,000 vibration cycles the preload attenuation rate is only 5%–8%, far better than nylon insert lock nuts.
• Wide temperature range: The all-metal structure is not limited by nylon aging and suits a wide temperature span from low to high; it only requires matching the appropriate base material and coating to suit various working conditions.
• Reusable: The metal insert structure allows repeated installation and removal, but the locking torque gradually decreases with the number of assemblies. Reuse beyond 5 times is not recommended.
• Easy installation: Installed directly onto the bolt like an ordinary hex nut, requiring no special tools or additional sealing elements.
• Cost-effective: Compared with nylon lock nuts and other complex anti-loosening solutions, the all-metal insert nut offers high cost-efficiency and is suitable for large-volume use.

III. Application Scope

• Automotive industry: Fastening of frequently vibrating components such as engine compartments, chassis suspension systems, and exhaust systems.
• Railway and rail transit: Critical joints in railway vehicle bogies, railroad switches, and locomotive diesel engines.
• Heavy machinery and construction equipment: Heavy-load vibration conditions in mining machinery, metallurgical equipment, vibratory rollers, excavators, and loaders.
• General mechanical equipment: Machine tools, printing equipment, packaging machinery, and other locations requiring anti-loosening fastening.
• Building steel structures: Fastening of steel-structure frames, curtain-wall installation, and other heavy-load structures.
• High-temperature equipment: Boilers, steam turbines, and other equipment operating under high-temperature vibration, where the all-metal structure carries no high-temperature failure risk.
• Other vibration scenarios: Aerial ropeways, wind turbine towers, and other settings with high demands on both anti-loosening and temperature resistance.