OEM manufacturer ASME B18.5 · DIN 603 · ISO 8677
Carriage Bolts — ASME B18.5 & DIN 603
Carriage bolts are round-head bolts with a square neck that locks into the joined material so the nut can be tightened from one side. Teshi Group manufactures carriage bolts to ASME B18.5 and DIN 603 / ISO 8677 in carbon steel and stainless steel.
Also called: coach bolts, round head square neck bolts, DIN 603 bolts, cup head bolts, mushroom head bolts
What are Carriage Bolts?
A carriage bolt, also called a coach bolt, has a smooth domed head with no drive feature and a short square neck beneath it. When drawn into a square hole in steel or bites into timber, the neck stops the bolt turning, so the nut is tightened from the far side only. The smooth head gives a tamper-resistant, snag-free face. Carriage bolts are used for timber-to-steel joints, cable trays, walkway grating, fencing and equipment guards.
Key features
- Round head, square neck to ASME B18.5 (inch) and DIN 603 / ISO 8677 (metric)
- Ribbed neck, fin neck and short neck variants on request
- Carbon steel grade 2 / grade 5, metric 4.6 and 8.8
- Stainless steel 304 (A2) and 316 (A4)
- Hot-dip galvanised or zinc plated for outdoor use
Specification
| Supply | OEM manufacturer — Teshi Group, India, India |
|---|---|
| Standard | ASME B18.5 (inch), DIN 603 / ISO 8677 (metric) |
| Head / neck | Round (mushroom) head; square, ribbed, fin or short neck |
| Carbon steel | SAE J429 Gr 2 and 5; ISO 898-1 class 4.6, 8.8 |
| Stainless steel | 304 / A2-70, 316 / A4-70 |
| Threads | UNC, ISO metric coarse |
| Finish | Plain, zinc electroplated, hot-dip galvanised |
| Testing | Tensile, hardness; PMI on stainless |
| Documents | EN 10204 3.1 mill test certificate (3.2 / third-party inspection when specified), dimensional inspection report |
Applications
- Cable tray and support installations
- Walkway grating and handrail fixing
- Timber-to-steel structures and pallets
- Machine guards and enclosures
- Fencing and gate hardware
FAQ
Carriage Bolts: common questions
What is the difference between a carriage bolt and a hex bolt?
A carriage bolt has a smooth domed head and square neck that stops it rotating, so it is tightened only from the nut side. A hex bolt needs a spanner on the head.
What hole is needed for a carriage bolt in steel?
In steel the square neck needs a square-punched hole of matching size to stop rotation. In timber a round hole is drilled and the neck is drawn in by tightening the nut.
Are carriage bolts available in stainless steel?
Yes. We supply 304 (A2) and 316 (A4) stainless steel carriage bolts for outdoor structures, coastal sites and chemical plants, along with matching stainless nuts and washers.
Can carriage bolts be hot-dip galvanised?
Yes. Carbon steel carriage bolts can be hot-dip galvanised for outdoor use such as grating, fencing and cable tray. Galvanised bolts are supplied with oversize-tapped galvanised nuts so the coated threads assemble freely.
Need a size or grade not listed here?
Our engineering team manufactures against your drawing or datasheet, with dimensional sign-off before dispatch.
Send us your specificationTraceability
From mill heat to your site
- 01
Approved mill material
Received against the mill certificate; heat number registered.
- 02
Forging & machining
Heat number carried through every stage in our Indian works.
- 03
PMI, dimensional & NDT
Every lot inspected to the governing standard; TPI witness on request.
- 04
Stamped & certified dispatch
Hard-stamped pieces with EN 10204 3.1 / 3.2 certificates.
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