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Carriage Bolts

Round Head Square Neck Bolts for Secure Through-Fastening

VALTOR supplies carriage bolts with a smooth round head and square neck design for applications requiring secure fastening and resistance to rotation during assembly. Available in stainless steel and carbon steel options, carriage bolts can be supplied in different diameters, lengths, materials and finishes according to project requirements.

Product
Carriage Bolts
Head Type
Round Dome Head
Neck Type
Square Neck
Materials
304 / 316 Stainless Steel · Selected Stainless Steel Grades · Carbon Steel
Thread
Metric / UNC / UNF
Diameter
Common and Custom Sizes Available
Length
Standard and Custom Lengths
Thread Configuration
Partial / Full Thread Depending on Size
Customization
Custom Diameter, Length, Material, Finish and Packaging Available

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Product Overview

Carriage bolts are round head fasteners featuring a square neck beneath the head that helps prevent the bolt from rotating when tightened with a nut. The square neck engages with the surrounding material, allowing the fastener to remain stable during installation without requiring access to hold the bolt head from turning.

VALTOR supplies stainless steel carriage bolts and carbon steel carriage bolts for applications requiring clean appearance, reliable fastening and straightforward installation. 304 stainless steel carriage bolts are suitable for many general corrosion-resistant assemblies, while 316 stainless steel carriage bolts can be selected for more demanding outdoor or moisture-exposed conditions. Carbon steel versions are available for general mechanical and structural fastening requirements.

Unlike conventional hex bolts that may require a wrench on both sides, round head square neck bolts are designed for through-fastening applications where the smooth external head provides a clean appearance and the square neck helps maintain the bolt position during tightening. Carriage bolts with square neck geometry are especially useful where access to the head side is limited.

Common applications include wood structures, outdoor furniture, metal fabrication, construction components, equipment frames and general assemblies. As a carriage bolts supplier and custom carriage bolts manufacturer, VALTOR can evaluate M8 stainless steel carriage bolts and other requested sizes according to diameter, length, material, thread configuration and surface finish.

Technical Specifications

Reference fields for carriage bolt purchasing; final dimensions and configurations should be confirmed against the application requirement.

Product Type
Carriage Bolts / Coach Bolts / Round Head Square Neck Bolts
Head Type
Round Dome Head
Neck Type
Square Neck
Material
304 Stainless Steel · 316 Stainless Steel · Selected Stainless Steel Grades · Carbon Steel
Thread
Metric · UNC · UNF
Diameter Range
Common Sizes Available · Custom Sizes Available
Length
Custom Length Available
Thread Configuration
Partial Thread / Full Thread Depending on Size
Surface Finish
Plain · Passivated · Polished · Brushed · Zinc Plated · Hot Dip Galvanized · Black Oxide
Customization
Custom diameter, length, material, finish and packaging available
Documentation
Material Certificates · Inspection Reports · Third-Party Inspection Available
No unrelated DIN bolt standard is assumed. Final dimensions, material, thread configuration and finish should be confirmed against the purchasing specification.

Round Head & Anti-Rotation Design

The smooth round head and square neck give carriage bolts their distinctive installation advantage.

1Round Dome Head — The smooth rounded head provides a clean external appearance and reduces exposed sharp edges compared with conventional hex head fasteners.
2Square Neck Locking Feature — The square neck beneath the head engages with the installation material and helps prevent the bolt from turning during tightening.
3Through-Fastening Installation — Carriage bolts are inserted through a pre-drilled hole and secured from the opposite side using a nut and washer.
4Material & Finish Options — Stainless steel and carbon steel options with different finishes are available according to corrosion resistance, appearance and application requirements.

Surface Finishes

Finish selection depends on material, service environment and appearance requirements.

Stainless Steel
PlainPassivatedPolishedBrushed
Carbon Steel
Zinc PlatedHot Dip GalvanizedBlack Oxide

Available finishes must be confirmed for the selected material, dimensions and operating environment.

Carriage Bolt Customization

VALTOR supports customized carriage bolts according to diameter, length, material, finish and packaging requirements. Customers can provide drawings, samples or application specifications for evaluation.

1Custom Dimensions — Different diameters, lengths and thread configurations can be supplied according to requirements.
2Material Selection — 304, 316 stainless steel and carbon steel options are available depending on application conditions.
3Surface Requirements — Different finishes can be provided according to corrosion resistance and appearance requirements.
4Packaging Options — Bulk packing and customer-specific packaging solutions are available for qualified orders.

Quality & Documentation

Documentation can be provided to support customer verification and traceability.

Material Test Certificate (MTC)
Raw Material Reports
Dimensional Inspection
Product Inspection Documentation
Third-Party Inspection

Availability & Delivery

Availability, sample feasibility and lead time depend on the requested dimensions, material and finish.

MOQ
Specification Based
Confirmed per inquiry
Samples
Available on Review
Depends on configuration
Standard Sizes
Check Availability
By size and material
Custom Production
Project Lead Time
Confirmed after review

Packaging & Private Label

Standard and customized packaging options for B2B supply.

Packaging Options
Paper BoxCartonWooden PalletBulk PackingWooden CaseCustomized Packaging
Private Label

Custom branded packaging is available for qualified customers. Customer brand logos and packaging can be produced after proper brand authorization.

Applications

Carriage bolts are used for secure through-fastening where a smooth external head, square-neck anti-rotation feature and reliable nut-side connection are required.

Stainless steel carriage bolt fastening a timber beam to a galvanized steel bracket with a washer and nut
01

Wood Structure Assembly

Carriage bolts for wood construction are commonly used in wooden structures, outdoor projects and timber connections where a smooth head appearance and secure fastening are required.

02

Outdoor Furniture & Equipment

The smooth round head design makes stainless steel carriage bolts suitable for outdoor furniture, frames and equipment assemblies where appearance and durability are important.

03

Metal Fabrication & Sheet Components

Carriage bolts can be used in fabricated metal assemblies where a clean external fastening appearance and secure mechanical connection are required.

04

Construction Components

Carriage bolts are used in selected construction and structural assemblies where components require reliable through-fastening connections.

05

Agricultural Equipment & General Machinery

Carriage bolts can be used in equipment frames, agricultural structures and general mechanical assemblies requiring secure fastening.

Frequently Asked Questions

What is the difference between carriage bolts and hex bolts?

Carriage bolts feature a smooth round head and square neck designed to resist rotation during tightening, while hex bolts use a wrench-driven hexagonal head.

How does the square neck of a carriage bolt work?

The square neck fits into the surrounding material and helps hold the bolt in position while the nut is tightened from the opposite side.

What materials are available for carriage bolts?

VALTOR supplies carriage bolts in stainless steel options including 304 and 316, as well as carbon steel configurations depending on application requirements.

Can carriage bolts be customized in different sizes and finishes?

Yes. Diameter, length, material, thread configuration, surface finish and packaging can be customized according to customer requirements.

Can samples be provided before bulk production?

Yes. Samples can be arranged for customers to verify dimensions, material and assembly suitability before larger production orders.

Need Custom Carriage Bolts for Your Project?

Share the required diameter, length, material, finish, application specification or drawing with VALTOR for evaluation and quotation.

Request A Quote




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