Carriage Bolts
Carriage bolts, also known as round head square neck bolts, have a smooth rounded head and a square neck directly below the head. When the bolt is installed through a matching hole, the square neck helps keep the bolt from turning while the nut is tightened. The rounded head also gives the exposed side of the connection a smooth profile, making this type of bolt useful where a projecting hexagonal head is not preferred.
The dimensions of carriage bolts vary between metric and inch-series standards. We manufacture metric carriage bolts according to DIN 603 and inch-series carriage bolts according to ASME B18.5, with stainless steel and carbon steel available for different requirements. The following sections provide dimensional standards, material and mechanical requirements, and other technical information to help with selecting the appropriate carriage bolt for an application.
Specification:
| Item | Metric Carriage Bolts | Inch Carriage Bolts |
|---|---|---|
| Size Range | M5-M20 | #10-1" |
| Dimension Standard | DIN603 | ASME B18.5 |
| Thread | ISO Metric Coarse,Fine Thread | UNC,UNF |
| Thread Standard | ISO 261, ISO 965 | ASME B1.1 |
| Thread Class | 6g | 2A |
| Material | Cabon Steel,Alloy Steel,Stainless Steel,Aluminum,Brass | Cabon Steel,Alloy Steel,Stainless Steel,Aluminum,Brass |
| Steel Property Class | ISO898-1,Class4.8,8.8,10.9,12.9 | SAE J 429 Grade2,5,8 |
| Stainless Steel Class | A2-70,A2-80,A4-70,A4-80 | F593C, F593D, F593G,F593H |
| Surface Treatment | Black Oxidation, Zinc Plated, HDG, Dacromet, Bright Finish,Passivation | |
| Inspection | Dimension,Thread,Mechanical Proeprty,Coating | |
Dimension Standard:
Carriage bolts are available in different dimensional standards for metric and inch-series applications. The two standards commonly used for our carriage bolts are DIN 603 for metric sizes and ASME B18.5 for inch-series sizes. Both standards define the main dimensions of the bolt, including the head, square neck, shank, thread, and length. The standard drawings below are provided as a quick reference.
DIN 603 Carriage Bolts
DIN 603 covers metric carriage bolts with a round head and square neck. Typical dimensions include M5, M6, M8, M10, M12, M16, and M20, with the required head diameter, head height, square neck dimensions, and thread length varying with the nominal diameter and bolt length.
ASME B 18.5 Carriage Bolts
ASME B18.5 covers inch-series round head bolts, including round head square neck bolts commonly known as carriage bolts. The standard defines the main dimensions of the bolt, including the head diameter, head height, square neck width and depth, and other features of the bolt head and shank. Dimensions are specified in inches and are based on the nominal bolt diameter.
Mechanical Proeprty:
The mechanical properties of carriage bolts depend on the material, grade, and applicable specification. For carbon steel and alloy steel carriage bolts, metric products can be specified according to ISO 898-1, while inch-series products can be supplied according to SAE J429. For stainless steel carriage bolts, ISO 3506-1 and ASTM F593 provide the relevant mechanical and material requirements for metric and inch-series products respectively.
For stainless steel applications, 304 stainless steel carriage bolts are commonly selected for general corrosion-resistant applications, while 316 stainless steel carriage bolts are used when greater resistance to corrosion is required. ASTM F593 specifically includes both 304/304L and 316/316L stainless steels among the covered alloy groups.
The table below summarizes the main mechanical property standards and grades applicable to our carriage bolts. Tensile strength, proof load or yield strength, elongation, and hardness are specified according to the selected material and grade.
| Mechanical Proeprty Standard | ISO 898-1 | SAE J429 | ISO 3506-1 | ASTM F593 |
| Property Class | Class4.8,8.8,10.9,12.9 | GR.5,8,10 | A2-70,A2-80,A4-70,A4-80 | F593 C, F593 D,F593 G,F593 H |
Quality control of Carriage Bolts:
Quality control is carried out throughout the production process to ensure that hex bolts meet the specified dimensional, mechanical and surface requirements. Depending on the product specification, inspections cover raw materials, dimensions, threads, mechanical properties, surface condition and final appearance before shipment. Inspection methods and acceptance criteria are selected according to the applicable standards and customer requirements.
| Inspect Item | Detail |
|---|---|
| Raw Material | We check the material grade and chemical composition against the specified requirements. Material certificates can be provided when required. |
| Dimensions | Critical dimensions such as bolt length, thread diameter, head width, head height, and flange diameter are checked against the applicable dimensional standard or customer drawing. |
| Thread Quality | Thread size, pitch, thread fit, and other thread requirements are checked with suitable gauges and measuring tools to ensure proper assembly. |
| Mechanical Properties | Tensile strength, yield or proof load, hardness, elongation, and other required properties are tested according to the specified material grade and performance standard. |
| Surface Finish | After surface treatment, we check the coating or finish for appearance, coverage, and other specified requirements. Available finishes include zinc plating, black oxide, zinc flake coatings, passivation, and other treatments according to the order. |
Related Bolt Products
In addition to carriage bolts, we also supply a wide range of bolt products for different fastening requirements and applications. Depending on the required head style, installation method, strength level, and application, customers can also consider hex bolts, heavy hex bolts, carriage bolts, flange bolts, stud bolts, U-bolts, anchor bolts, and T-bolts. Explore our complete range of bolts to find the appropriate fastening solution for your project.