Application guide for Square Nuts to DIN 557. The core duty of the type is channel, strut and woodwork where a non-rotating, large-bearing nut is needed. The typical industries, the how-to-specify checklist, assembly practice and the exclusion cases are set out below. Stocked across roughly M5 to M20, they cover general to heavy-duty work.
Typical Applications for Square Nuts
The most common settings where these are specified:
- Bolted joints: the clamping counter-face on studs and bolts across every assembly type.
- Vibration-prone equipment: where a locking or flanged style resists loosening.
- Frames & weldments: captive or welded options for repeatable assembly.
- Strut & channel systems: sliding into channel where the flats stop rotation.
- Woodworking: large-bearing nuts seated into timber.
How to Specify Square Nuts for Your Application
- Size: Match the nominal size to the mating thread or hole. This product spans M5–M20; 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 DIN 557. 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 Square Nuts
- 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 Square Nuts 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.