DIN 478 Square Head Bolts with Collar
DIN 478 square head bolts with collar, M5 to M24 — the square head that a wrench cannot spin off, with a machined collar bearing face — with the full collected 10-column table: pitch, thread-length bands, collar and shank limits, head height and width across flats/corners.
Last updated: 2026-11
Specifications
DIN 478 is the square head bolt finished with a cylindrical collar under the head: the square head gives a spanner a full flat on each of four sides and resists turning back in the hand, while the collar provides a turned bearing face that seats cleanly on the clamped part instead of the as-forged underside of a plain square head. That combination suits rough construction, clamp fixtures, agricultural and mining equipment — anywhere the head is set with a straight spanner in tight quarters and the joint wants a stable seat. The collected table covers M5 to M24 in the source's three column groups, with pitch P, the thread-length bands b (tolerance printed by the source as "+2P，0") for bar lengths up to and over 125 mm, chamfer c min/max, collar diameter d c, shank d s, head height k, width across flats s and across corners e — each with its max/min limits. Some sizes appear in two columns with different across-flats (M16 at s 16 and 17, M20 at s 21 and 22): both are printed by the source and reproduced verbatim. Materials, property classes and finishes are not printed by the collected specification and stay per RFQ.
| Standard | DIN 478 — square head bolts with collar (raised cylindrical bearing face under a square head) |
|---|---|
| Series | M5 – M24 (tabulated in the source's three column groups; M16 and M20 each printed in two across-flats variants) |
| Tabulated geometry | Per size: pitch P, thread length b (+2P，0, split at L 125 mm), chamfer c (min/max), collar d c (max/min), shank d s (max/min), head height k (min/max), across flats s (max/min), across corners e (max/min) |
| Function | Four-flat square head for spanner wrenching; collar gives a machined seat instead of a forged head underside |
| Materials / strength | Not tabulated by the collected specification — per RFQ (property class per clamping load) |
| Size | P | b (+2P，0) — L ≤ 125 | b (+2P，0) — L ＞ 125 | c — min | c — max | d c — max=nominal size | d c — min | d s — max=nominal size | d s — min | k — min | k — max | s — max=nominal size | s — min | e — max=nominal size | e — min |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| M5 | 0.8 | 16 | - | 1.88 | 2.12 | 9.5 | 8.92 | 5 | 4.82 | 6.82 | 7.18 | 5 | 4.82 | 6.5 | 5.92 |
| M6 | 1 | 18 | - | 1.88 | 2.12 | 10.5 | 9.8 | 6 | 5.82 | 7.82 | 8.18 | 6 | 5.82 | 8 | 7.42 |
| M8 | 1.25 | 22 | - | 1.88 | 2.12 | 13.5 | 12.8 | 8 | 7.78 | 9.82 | 10.18 | 8 | 7.78 | 10 | 9.42 |
| M10 | 1.5 | 26 | 32 | 2.88 | 3.12 | 16.5 | 15.8 | 10 | 9.78 | 12.78 | 13.22 | 10 | 9.78 | 13 | 12.3 |
| M12 | 1.75 | 30 | 36 | 2.88 | 3.12 | 19.5 | 18.66 | 12 | 11.73 | 14.78 | 15.22 | 13 | 12.73 | 17 | 16.3 |
| M16 (s 16) | 2 | 38 | 44 | 3.85 | 4.15 | 25 | 24.16 | 16 | 15.73 | 19.74 | 20.26 | 16 | 15.73 | 21 | 20.16 |
| M16 (s 17) | 2 | 38 | 44 | 3.85 | 4.15 | 25 | 24.16 | 16 | 15.73 | 19.74 | 20.26 | 17 | 16.73 | 22 | 21.16 |
| M20 (s 21) | 2.5 | 46 | 52 | 4.85 | 5.15 | 31 | 30 | 20 | 19.67 | 24.74 | 25.26 | 21 | 20.67 | 27 | 26.16 |
| M20 (s 22) | 2.5 | 46 | 52 | 4.85 | 5.15 | 31 | 30 | 20 | 19.67 | 24.74 | 25.26 | 22 | 21.67 | 28 | 27.16 |
| M24 | 3 | 54 | 60 | 5.85 | 6.15 | 36 | 35 | 24 | 23.67 | 27.74 | 28.26 | 24 | 23.67 | 32 | 31 |
Materials
- Material and property class specified per RFQ — confirm against clamping load at quotation
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 478 Square Head Bolts with Collar) 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 1,000–10,000 pieces depending on size. Stock items run 3–7 days. High-strength and custom parts run 15–25 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
When is the collared DIN 478 the right square head bolt?
When the seat matters as much as the head. A plain square head bolt (DIN 479/480 forms excepted) bears on its as-forged underside, which is fine on timber and rough steelwork but rocks on machined surfaces. The DIN 478 collar is a turned cylindrical face, so the bolt sits flat on machined pads and clamps without brinelling the part — the usual choice on fixtures, machine frames and any joint where the clamped face is finished. The square head itself is worth keeping where access is awkward: a spanner engages four flats at any quarter turn and the head will not round off the way a worn hex can. Check the collected table's across-flats column against your wrench set — the source prints two s values for M16 and M20, so confirm which wrench population the joint must match before ordering.
What is the MOQ and lead time for this bolt type?
The minimum order quantity is 1,000–10,000 pieces depending on size. Stock items ship in 3–7 days; high-strength and custom parts in 15–25 days. Common diameters in this bolt type are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
Related knowledge
- What Bolt Property Classes 8.8, 10.9 and 12.9 Encode — and When High Strength Stops Being the Right Choice
- Bolt Grade Selection: ISO 898-1 8.8/10.9/12.9 vs ASTM A307 and A325
- 8.8 vs 10.9 vs 12.9 Bolts: Strength, Hardness and Cost — What the Evidence Settles
- Calculating Bolt Preload and Clamp Force: Torque, Friction and Tightening Method
- How to Determine Tightening Torque and Choose a Tightening Method for a Bolted Joint
- Fastener Failure Modes: Which Fatigue, Creep and SCC Controls the Evidence Supports
- Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ
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