Material
Stainless Steel
Type
Cup head, square neck
Size Range
M6–M20
Surface Finish
Plain / Passivated
Grade
4.8 / 8.8 / A2 / A4
Standard
DIN 603 / ISO 8677
Packaging
Carton / Pallet
MOQ
1 piece (sample)
Precision Manufacturing, Batch After Batch
From cold-heading raw steel wire to heat-treated finished bolts, every step runs under strict in-house process control — ensuring the dimensional accuracy and strength grade printed on every head marking.
Product Overview
Application Scenarios
Carriage bolts (DIN 603), also called coach or cup-square bolts, have a smooth domed head over a square neck and a metric thread. Dropped through a round hole, the square neck pulls into the timber or a matching square hole and locks the bolt against turning, so it can be tightened from the nut side alone with no tool on the head. The low, smooth head leaves nothing to snag and resists tampering. They are the standard fixing for timber structures, decking, fencing, playground and agricultural equipment, steel-to-wood brackets, machine guards and trailer bodies. Hot-dip galvanized and stainless versions suit outdoor, ground-contact and marine use.
Installation Notes
Drill a clearance hole the same nominal diameter as the bolt; in timber the square neck bites the wood as it is drawn in, while in metal a matching square hole seats the neck. Seat the head by tapping it home until the square pulls fully below the surface, then tighten the nut against a flat washer on the reverse — the head needs no wrench. Do not over-tighten in softwood or the neck will spin in an enlarged hole. Use hot-dip galvanized or A4 stainless for exposed, wet or ground-contact joints, and a nylon-insert or spring washer where vibration is present.
Material & Certification
Cold-formed from austenitic stainless steel — A2 (AISI 304) or A4 (AISI 316) — to DIN 603 and ISO 3506, with the square neck and cup head gauge-checked and every batch traceable to raw material certificates. Each lot passes dimensional inspection before packaging; EN 10204 3.1 material certificates are available on request.
Carriage Bolt
Stainless Carriage Bolt · A2 / A4 · 304 / 316 · DIN 603
Dimensional Specifications
DIN 603 / ISO 8677 Standard Reference Dimensions — click a size to locate it below
| Thread Size | Head Dia dk (mm) | Head Height k (mm) | Square Neck v (mm) |
|---|---|---|---|
| M6 | 16 | 3.5 | 6 |
| M8 | 20 | 4.5 | 8 |
| M10 | 24 | 5.0 | 10 |
| M12 | 30 | 6.5 | 12 |
| M16 | 38 | 8.5 | 16 |
| M20 | 46 | 10.5 | 20 |
Reference dimensions per DIN 603 / ISO 8677. Full size range M6–M20 available on request — contact us for custom specification sheets.
Applications
Construction
Steel structures, bridges, buildings, concrete anchors
Machinery
Heavy equipment, industrial machines, manufacturing
Infrastructure
Railways, towers, pipelines, power transmission
Automotive
Vehicle assembly, chassis, engine components
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