Nylon Insert Hex Lock Nut (GB/T 889 / ISO 7040) are specified where the joint requires the clamped counter-face of a bolted joint. The sections below cover the typical end-uses by industry, the size and material decisions for each, assembly practice, and the applications this fastener type is not suited to. Stocked across roughly M3 to M36, they cover general to heavy-duty work.
Typical Applications for Nylon Insert Hex Lock Nut — GB/T 889 / ISO 7040 (Series 078)
The most common settings where these are specified:
- Vibration-prone equipment: where a locking or flanged style resists loosening.
- Frames & weldments: captive or welded options for repeatable assembly.
- General machine building: fastening covers, brackets, motors and sub-assemblies on production equipment.
- Maintenance & repair (MRO): a stocked size for servicing existing plant where the original fastener spec must be matched.
- Fabrication & metalwork: bench and on-site assembly of steel frames, enclosures and weldments.
How to Specify Nylon Insert Hex Lock Nut — GB/T 889 / ISO 7040 (Series 078) for Your Application
- Size: Match the nominal size to the mating thread or hole. This product spans M3–M36; check the full table below for the exact dimensions of each size.
- Locking & grade: Match the strength grade to the bolt, and choose a locking style (nyloc, all-metal, serrated flange) if the joint sees vibration.
- Environment: For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient.
- Standard: This product is supplied to GB/T 889 / ISO 7040. Quoting the standard on your order guarantees interchangeable dimensions between suppliers.
Installation & Assembly Practice
- Run the nut down by hand before applying the wrench to catch cross-threading early.
- Tighten the nut rather than the bolt head where access allows — the torque-to-preload relation is more consistent.
- For locking styles, note that nyloc inserts are single-use in critical joints and lose grip above roughly 120 °C.
Common Selection Mistakes with Nylon Insert Hex Lock Nut — GB/T 889 / ISO 7040 (Series 078)
- Pairing a high-class bolt with a lower-class nut — the nut strips before the bolt reaches proof load; the nut class must meet or exceed the bolt class.
- Using a plain nut with a spring washer in severe vibration instead of a prevailing-torque locking nut.
- Re-using nyloc nuts in critical joints.
Where Nylon Insert Hex Lock Nut — GB/T 889 / ISO 7040 (Series 078) Are Not the Right Choice
Not on their own — they need a matching bolt or stud — and a plain nut is not a substitute for a locking type under heavy vibration.