DIN 557 Square Nuts
DIN 557 square nuts, M5 to M16 — the four-sided nut for recesses, channels and antique-look assemblies — with the full collected 8-size table: corner and flat widths, nut and nib heights, and the source's reference mass per 1000 units.
Last updated: 2026-11
Specifications
DIN 557 is the square nut — four flats at 90 degrees instead of six — surviving in modern work for exactly the situations its shape fits: it sits captively in a square recess or channel where a hex nut would rotate in place, its corners give a wrench four positions instead of two in tight quarters, and it is the period-correct choice for restored machinery and architecture. The collected table runs M5 to M16 with the d w bearing-face minimum, e across-corners max/min, the m nut height pair, the m 1 nib height minimum, the s across-flats limits, and the source's reference mass per 1000 units. Where two widths exist for one thread (M10 SW 16, M12 SW 18 — the source's own size labels), the table carries them as separate rows. Note that the source prints "l3" in the M16 m max cell — a printed typo for 13, reproduced verbatim and flagged rather than silently corrected. The washer-faced and heavy square forms belong to other DIN designations; on this site the hex counterpart for general use is DIN 934. Materials, property classes and finishes are not printed by the collected specification and stay per RFQ.
| Standard | DIN 557 — square nuts |
|---|---|
| Series | M5 – M16 (8 sizes tabulated, including the M10 SW 16 and M12 SW 18 width variants) |
| Tabulated geometry | Per size: pitch P, bearing face d w min, across-corners e max/min, nut height m (max=nominal size / min), nib height m 1 min, across-flats s (max=nominal size / min), reference mass per 1000 units ≈ kg |
| Head form | Square nut — four 90° flats, sits captively in square recesses and channels |
| Family note | Hex counterpart for general use DIN 934; the M16 m max cell prints "l3" in the source (typo for 13 — reproduced verbatim) |
| Materials / strength | Not tabulated by the collected specification — per RFQ (property class and finish per drawing callout) |
| Nominal thread | P — Pitch | d w — min | e — max | e — min | m — max=nominal size | m — min | m 1 — min | s — max=nominal size | s — min | per 1000 units ≈ kg |
|---|---|---|---|---|---|---|---|---|---|---|
| M5 | 0.8 | 6.7 | 11.3 | 9.93 | 4 | 3.52 | 2.5 | 8 | 7.64 | 1.31 |
| M6 | 1 | 8.7 | 14.1 | 12.53 | 5 | 4.52 | 3.2 | 10 | 9.64 | 2.77 |
| M8 | 1.25 | 11.5 | 18.4 | 16.34 | 6.5 | 5.92 | 4.1 | 13 | 12.57 | 5.5 |
| M10 | 1.5 | 14.5 | 22.6 | 20.24 | 8 | 7.42 | 5.2 | 16 | 15.57 | 10.7 |
| M10 SW 16 | 1.5 | 15.5 | 24 | 21.54 | 8 | 7.42 | 5.2 | 17 | 16.57 | 13 |
| M12 | 1.75 | 16.5 | 25.4 | 22.84 | 10 | 9.42 | 6.6 | 18 | 17.57 | 16.3 |
| M12 SW 18 | 1.75 | 17.2 | 26.9 | 24.02 | 10 | 9.42 | 6.6 | 19 | 18.48 | 19.1 |
| M16 | 2 | 22 | 33.9 | 30.11 | l3 | 12.3 | 8.6 | 24 | 23.16 | 38.2 |
Materials
- Material, property class and finish specified per RFQ — the collected specification table covers geometry and reference mass only
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (DIN 557 Square Nuts) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Why choose a square nut over a hex nut?
For the recess, not for the wrench. A square nut fills a square pocket completely, so it cannot spin while the bolt is tightened from the other side — the standard way to fasten into wooden gates, cast channels and furniture frames without holding the nut. The 90-degree corners also let a wrench re-grip four times per revolution in tight quarters. What you give up: a hex nut loads six flats instead of four, so corner wear and rounding starts sooner under the same torque, and modern torque specs are written around hex series s values — match the s column to your tooling, not the other way round.
What is the MOQ and lead time for this nut type?
The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days; non-stock items are confirmed at quotation. Common diameters in this nut type are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support