Still Confusing GB5780, GB5782 and DIN912? The 1mm Mistake Every Fastener Buyer Makes!

If you source hex bolts from China, you've probably seen quotes full of codes — GB5780, GB5782, DIN912 — and wondered whether they're interchangeable. They often are, but the small print (literally 1 mm of it) is where buyers get burned. As a bolt factory, here's the plain version.

Hex head bolts: what each code means

• GB5780 – hex head, half-thread, Grade C. Upgrade to GB5782 (Grade A/B) for tighter tolerance.

• GB5781 – hex head, full-thread, Grade C. Upgrade to GB5783 (Grade A/B).

• GB5784 – hex socket wood screw, thin shank, half-thread.

Grades A/B are simply more precise than C — when your project needs it, spec the upgrade.

The 1 mm / 2 mm trap (across-flats width)

This is the part that causes "why won't this bolt fit?" moments:

Rule of thumb: new GB is 1 mm narrower than old GB on M8–M14, and 2 mm wider than both old GB and DIN on M22. Head thickness differs slightly too, but it's usually interchangeable unless your design is strict.

Hex nuts

GB6170 is the "thick nut"; GB6172 is thinner; GB52 and DIN934 are standard. Across-flats: M8 nut is 13 mm (GB52 = 14 mm); on M10/M12/M14, DIN & GB52 run 1 mm wider than GB6170/6172; on M22, DIN934 & GB52 are 32 mm while GB6170/6172 are 34 mm. Other sizes are universal.

Hex socket (Allen) & carriage screws

• GB70-85 fully matches DIN912 — no difference in use. GB70-76 has a slightly smaller cap (e.g. M8: 12.5 vs 13.27 mm), so check cap diameter before substituting.

• Carriage screws: GB12 (small) < GB14 (large) < DIN603. For a big, thick head and neck, DIN603 is the safe choice.

Why this matters to your order

Mixing standards silently changes fitment and strength. We're a bolt factory supplying European distributors and OEMs, and we accept custom orders — send us your code, drawing, or sample and we'll match it, cross-reference GB↔DIN, prototype, and quote. Every batch ships with an MTC on request.

Contact us now for samples: support1@tianyufasteners.com. Explore our offerings at www.tianyufasteners.com.

Procurement Q&A

Q: Can you supply both GB and DIN standard fasteners? A: Yes. We produce hex bolts, nuts, socket-head and carriage screws to both GB and DIN specs, and we cross-reference grades for you (e.g. GB5780 ↔ GB5782) so your Bill of Materials stays consistent.

Q: How do you handle the 1 mm across-flats difference between GB and DIN? A: We print the exact across-flats dimension on every quote. Tell us which standard your assembly is built to, and we'll match it — so your wrenches and seating always fit.

Q: Can you make non-standard or custom-grade bolts? A: Yes. As a factory we accept custom orders: send a drawing, sample, or even a photo of the spec code, and we'll produce to your requirement with full inspection.

Q: What documents come with the shipment? A: Every batch includes a Material Test Certificate, and we can provide dimensional inspection and salt-spray reports on request to support your European compliance file.