Square Nuts
A four-sided metric nut manufactured to DIN 557, with flat faces that lock against channels, slots and adjacent surfaces so the nut cannot turn while the bolt is tightened. Available in Class 5 steel and SS 304 stainless steel in metric coarse sizes M5 to M16. Ready stock in Bengaluru.
What is a Square Nut?
A square nut is a four-sided internally threaded fastener that mates with a bolt or machine screw to clamp components together. Its four flat sides give a larger bearing surface against the part than a hex nut of the same thread size, and they sit flush against the wall of a channel, slot or pocket — so the nut holds itself against rotation and can be tightened from the bolt side alone. This makes it the standard choice for blind and one-sided assembly, slotted framing and sheet-metal enclosures. Manufactured to DIN 557 (product grade C) with a chamfer on one face, square nuts are stocked in Class 5 steel and SS 304 stainless steel.
Standards & Specifications
Square nuts are manufactured to the following standards, covering dimensions, mechanical properties and thread form:
- DIN 557 — Square nuts, product grade C. Defines width across flats, width across corners and nut thickness for metric coarse thread sizes M5 to M16, chamfered on one face.
- Property Class 5 — Mechanical properties for the carbon steel nuts as called up by DIN 557.
- ISO 3506 — A2 — Material designation for the SS 304 austenitic stainless steel nuts.
- ISO 261 / ISO 965 — ISO metric coarse thread form; thread tolerance class 7H for product grade C nuts.
Technical Drawing &
Dimensional Tolerances
| Size | Pitch (P) | A/F — s (mm) | A/C — e min (mm) | Thickness — m (mm) |
|---|---|---|---|---|
| M5 | 0.80 | 8.00 | 10.60 | 4.00 |
| M6 | 1.00 | 10.00 | 13.20 | 5.00 |
| M8 | 1.25 | 13.00 | 17.20 | 6.50 |
| M10 | 1.50 | 17.00 | 22.50 | 8.00 |
| M12 | 1.75 | 19.00 | 25.10 | 10.00 |
| M16 | 2.00 | 24.00 | 31.70 | 13.00 |
All dimensions in mm per DIN 557 — Product Grade C. Thread tolerance class 7H. Key: s = across flats · e = across corners · m = thickness.
Sizes Available
Square nuts are stocked in the full DIN 557 range, M5 to M16, in both Class 5 steel and SS 304. All sizes are metric coarse pitch.
| Size × Pitch | Steel Class 5 | SS 304 |
|---|---|---|
| M5 × 0.8 | ✓ | ✓ |
| M6 × 1.0 | ✓ | ✓ |
| M8 × 1.25 | ✓ | ✓ |
| M10 × 1.5 | ✓ | ✓ |
| M12 × 1.75 | ✓ | ✓ |
| M16 × 2.0 | ✓ | ✓ |
Applications
Square nuts are used wherever the nut has to stay put without a spanner on it — dropped into a channel, slid into a slot or seated in a pocket — and wherever a wider bearing face is needed on soft or thin material.