Carriage Bolts Manufacturer in India
Jade Alloys is a carriage bolts manufacturer and supplier in India. A carriage bolt is made for joints that can only be tightened from one side. The smooth domed head gives nothing for a spanner to grip. Instead, the square shoulder under the head does the work. As the nut is drawn up, that square section pulls into the timber or seats in a punched square hole and holds the bolt still. We forge this fastener in two head forms and six neck profiles. Each one is matched to how hard the joint must resist pull-through and spin, from furniture and decking to bridge, dock and highway structures.
We match the material to the job. For general work we hold ready stock in carbon steel Grade 2, 5 and 8, stainless steel 304 and 316, and alloy steel. For corrosive or high-heat service we forge to order in Duplex and Super Duplex, Inconel, Hastelloy and Monel. The same part is also sold as a coach bolt, timber bolt, track bolt or mushroom head bolt. Every batch leaves our works with an EN 10204 3.1 test certificate and ships to the Gulf, Southeast Asia and Europe.
What is a Carriage Bolt
A carriage bolt is a round head, square neck bolt with a unified or metric thread. Where a standard bolt threads close to the head, the carriage bolt carries a short square shoulder directly under a shallow dome head, followed by a plain cylindrical shank. That square neck is the whole point of the design: it bites into wood or locks into a square hole so the bolt cannot rotate, letting an installer run the nut up without reaching the head. The low dome also leaves a clean, tamper-resistant face on the show side, which is why carriage bolts are chosen for benches, railings, playground equipment and any assembly accessed or seen from one face only.
Types of Carriage Bolts We Manufacture
Carriage bolts are produced with different neck and head profiles, each giving a different resistance to pull-through and rotation:
Round Head Square Neck
The standard carriage bolt for timber and general construction.
Round Head Short Neck
A shorter square shoulder for sheet metal where a full neck would obstruct.
Round Head Ribbed Neck
Serrated ribs that grip soft metals, wood and plastics.
Fin Neck
Two opposed fins for thin plywood and soft materials.
Flat Head Square Neck
A low-profile countersunk head, used in the garage-door industry.
Oval & Elliptical Neck
For specialised anti-rotation requirements.
Related bolts we also manufacture include hex bolts, eye bolts, J bolts, U bolts, anchor bolts, elevator bolts and hanger bolts.
Carriage Bolt Specifications & Properties
| Property | Details |
|---|---|
| Product Type | Carriage Bolt (round head, square neck, anti-rotation) |
| Manufacturing | Hot Forged / Cold Forged |
| Metric Size | M3 to M72 (up to M160 on request) |
| Imperial Size | 1/4″ to 3″; lengths 3/8″ to 8″ |
| Threads | Metric (coarse/fine), UNC, UNF, BSW, ISO |
| Head Types | Round / Dome, Flat |
| Neck Types | Square, Short, Ribbed, Fin, Oval, Elliptical |
| Form | Fully Threaded / Partially Threaded |
| High-Tensile Grades | Grade 5, Grade 8, Class 12.9, 14.9 |
| Standards | ASTM, ASME, DIN, ISO, BS, IS, SAE, UNI, PN, EU |
Carriage Bolt Dimensions (ASME B18.5 Round Head, Square Neck)
Key head and neck dimensions for round head square neck carriage bolts (maximum values, in inches). Length is measured from the underhead bearing surface to the end of the bolt.
| Size | Body Dia | Head Dia (A) | Head Ht (H) | Sq Width (O) | Sq Depth (P) |
|---|---|---|---|---|---|
| No. 8 | 0.164 | 0.328 | 0.102 | 0.169 | 0.108 |
| No. 10 | 0.190 | 0.436 | 0.114 | 0.199 | 0.125 |
| No. 12 | 0.216 | 0.500 | 0.149 | 0.215 | 0.135 |
| 1/4″ | 0.250 | 0.594 | 0.145 | 0.260 | 0.156 |
| 5/16″ | 0.3125 | 0.719 | 0.176 | 0.324 | 0.187 |
| 3/8″ | 0.375 | 0.844 | 0.208 | 0.388 | 0.219 |
| 7/16″ | 0.4375 | 0.969 | 0.239 | 0.452 | 0.250 |
| 1/2″ | 0.500 | 1.094 | 0.270 | 0.515 | 0.281 |
| 5/8″ | 0.625 | 1.344 | 0.344 | 0.642 | 0.344 |
| 3/4″ | 0.750 | 1.594 | 0.406 | 0.768 | 0.406 |
Carriage Bolt Sizes & Standards
Every carriage bolt is made to a published specification. See our full Fastener Standards library, including ASTM, ASME, DIN, ISO and BS.
| Standard | Size Range |
|---|---|
| ASME B18.2.1 | 3/8″ to 3″ |
| ASME B18.2.3.6M | M12 to M36 |
| ASME B18.2.3.7M | M16 to M36 |
| ASTM A193 / A194 | M6 to M72 |
| DIN 603 / DIN 6914 | M6 to M72 |
| ISO 4032 / ISO 7412 | M12 to M36 |
| UNI 5712 / DIN-EN 14399-4 | M12 to M36 |
| BS 1769 | 1/2″ to 2″ |
| IS 1363 | M6 to M72 |
Carriage Bolt Materials & Grades
We produce carriage bolts across the full material range, from carbon steel and alloy steel to stainless steel and exotic alloys:
| Material | Grades |
|---|---|
| Stainless Steel | 304, 304L, 304H, 309S, 310S, 316, 316L, 316Ti, 316H, 317L, 321, 347, 904L; A2-70, A4-80, 18-8 |
| Carbon Steel | AISI 1006 to 1050; Grade 2, Grade 5, Grade 8 |
| Alloy Steel | A/SA 193 & 194 – B6, B7, B7M, B16, 2, 2H, Gr 7, Gr 8 |
| Duplex & Super Duplex | UNS S31803, S32205, S32550, S32750, S32760 |
| Inconel / Incoloy | 600, 601, 625, 718, 800, 800H/HT, 825, X-750 |
| Hastelloy / Monel | C-22, C-276, C-2000, B2, X / Monel 400, K500 |
| Others | Nickel 200/201, Titanium, Brass, Copper-Nickel, Nitronic, Nimonic, Bronze |
Carriage Bolt Mechanical Properties by Grade
Typical mechanical properties for carbon and stainless carriage bolts (1/4″ to 1″ diameter):
| Grade | Proof Load | Yield (min) | Tensile (min) | Hardness |
|---|---|---|---|---|
| Low Carbon | 33,000 psi | 36,000 psi | 60,000 psi | Rockwell B70 to B100 |
| Grade 5 | 85,000 psi | 92,000 psi | 120,000 psi | Rockwell C25 to C34 |
| Grade 8 | 120,000 psi | 130,000 psi | 150,000 psi | Rockwell C33 to C39 |
| Stainless 18-8 | – | 65,000 psi | 100,000 to 150,000 psi | Rockwell B95 to C32 |
Carriage Bolts Specification
Carriage Bolt Coatings & Finishes
To match the operating environment and extend service life, carriage bolts are supplied with the following finishes:
- Hot-Dip Galvanized (HDG)
- Zinc Plated (clear / blue / yellow / black)
- Zinc Cobalt & Aluminium-Zinc Flake
- PTFE / Xylan Coated
- Black Phosphate & Black Oxide
- Nickel Plated
- Polished / Passivated Stainless
- Plain / Self-colour
Carriage Bolt Applications
- Construction & Infrastructure: docks, bridges, highways, decks and structural timber framing.
- Furniture & Woodwork: timber joints, benches, playground equipment and fixtures.
- Industrial Machinery: securing frames, guards and load-bearing assemblies.
- Automotive: chassis, body and trailer components.
- Marine & Outdoor: galvanized and stainless bolts for corrosive, wet environments.
Why Choose Jade Alloys as Your Carriage Bolt Supplier
Established in 1985, Jade Alloys is an ISO 9001:2015 certified fastener manufacturer with full in-house control from raw material to finished carriage bolt. Every order ships with Mill Test Certificates to EN 10204 3.1 and optional SGS / TUV / BV inspection. Check our Bolts Weight Chart, Nuts Weight Chart and Metal Weights Calculator to estimate quantities, or download our catalogue and quality certificates.
FAQs – Carriage Bolt
What is a carriage bolt used for?
Why does a carriage bolt have a square neck?
What sizes do carriage bolts come in?
Which carriage bolt material is best for outdoor use?
Request a Carriage Bolt Quote
Send your size, material and quantity requirement for a same-day carriage bolt quotation. Request a Quote or email sales@jadealloys.com.
