Hex Bolt Manufacturer and Supplier

We manufacture and supply hex bolts, hex head screws, heavy hex bolts and structural bolts for industrial machinery, steel structures, oil and gas equipment, marine systems, valves, pumps and general engineering applications.

Our hex bolts are available in carbon steel, alloy steel and stainless steel, with metric or inch threads, full or partial threading and multiple corrosion-resistant coatings.

Products can be manufactured according to ISO 4014, ISO 4017, ASME B18.2.1, ASME B18.2.6, ASTM A307, ASTM A449 and ASTM F3125/F3125M, as well as customer drawings and project specifications.

Available grades include:

• Property Class 4.6, 5.8, 8.8, 10.9 and 12.9
• Stainless steel A2-70, A4-70 and A4-80
• ASTM A307 carbon steel
• ASTM A449 heat-treated alloy steel
• ASTM F3125 Grade A325 and A490 structural bolting
• ASTM A193 B7, B8 and B8M
• ASTM A320 L7 low-temperature bolting

Hex bolts can be supplied complete with compatible hex nuts, heavy hex nuts, flat washers and hardened structural washers.

Hex Bolt Supply Range

What Is a Hex Bolt?

A hex bolt is an externally threaded fastener with a six-sided head that can be tightened using a wrench or socket.

Hex bolts are generally installed with a matching nut and may also be used with flat washers, spring washers or hardened structural washers.

A hex bolt is normally specified by:

1. Dimensional standard
2. Nominal diameter
3. Thread pitch
4. Bolt length
5. Thread length
6. Material or property class
7. Surface coating
8. Matching nut and washer
9. Certification requirements

The dimensional standard defines the bolt geometry, while the material standard or property class defines its chemical, mechanical and heat-treatment requirements.

Hex Bolt Product Types

Partially Threaded Hex Bolts

A partially threaded hex bolt has an unthreaded shank between the underside of the head and the threaded portion.

The unthreaded section can provide a controlled grip area through the connected components and may help keep threads away from the primary shear plane.

Metric partially threaded hex bolts are commonly supplied according to ISO 4014.

Typical applications include:

• Industrial machinery
• Steel frames
• Equipment supports
• Pumps and valves
• Marine equipment
• Fabricated assemblies

Fully Threaded Hex Bolts

A fully threaded hex bolt has threads extending along most of the shank.

Metric fully threaded products are commonly manufactured according to ISO 4017 and are also commercially described as hex head screws.

Fully threaded bolts are suitable for:

• Thin connected components
• Short grip lengths
• Tapped holes
• Adjustable clamping positions
• General industrial assembly

Heavy Hex Bolts

A heavy hex bolt has a larger head width and bearing surface than a regular hex bolt of the same nominal diameter.

Heavy hex bolts are commonly used for:

• Structural steel connections
• Pressure equipment
• Large machinery
• Foundation assemblies
• High-load industrial joints

Regular hex bolts and heavy hex bolts are not dimensionally interchangeable. The applicable dimensional standard must be stated in the purchase order.

Structural Bolts

Structural bolts are high-strength fasteners designed for steel-to-steel structural connections.

Common structural bolt grades include:

• ASTM F3125 Grade A325
• ASTM F3125 Grade A490
• ASTM F3125 Grade A325M
• ASTM F3125 Grade A490M

Structural bolts are normally supplied as coordinated assemblies with compatible heavy hex nuts and hardened washers.

Custom Hex Bolts

Custom hex bolts can be manufactured according to drawings or equipment specifications.

Available custom features include:

• Large diameters
• Extended lengths
• Special thread lengths
• Reduced shanks
• Drilled heads or shanks
• Metric fine threads
• Special UNC or UNF threads
• Left-hand threads
• Special materials
• Custom head dimensions
• Project-specific marking
• Controlled coating thickness

Hex Bolt Materials and Grades

Carbon Steel Hex Bolts

Carbon steel hex bolts are widely used for general industrial, construction and machinery applications.

Common grades include:

• Property Class 4.6
• Property Class 5.8
• Property Class 8.8
• ASTM A307 Grade A
• ASTM A307 Grade B

Carbon steel bolts can be supplied with zinc plating, hot-dip galvanizing, black oxide, phosphate, zinc flake or fluoropolymer coatings.

Alloy Steel Hex Bolts

Alloy steel hex bolts are used where higher tensile strength, improved hardenability or special temperature performance is required.

Common grades include:

• Property Class 10.9
• Property Class 12.9
• ASTM A449
• ASTM F3125 Grade A490
• ASTM A193 Grade B7
• ASTM A320 Grade L7

The correct grade must be selected according to the joint design, service temperature, required preload, coating process and applicable engineering specification.

Stainless Steel Hex Bolts

Stainless steel hex bolts are used where resistance to moisture, chemicals, atmospheric exposure or cleaning processes is required.

Common grades include:

• A2-70
• A2-80
• A4-70
• A4-80
• ASTM A193 B8
• ASTM A193 B8M
• 304 stainless steel
• 316 and 316L stainless steel

A4 and 316-type stainless steels generally provide better resistance in many chloride-containing environments than A2 or 304-type materials. However, no stainless steel grade should be considered universally resistant to seawater or chemical corrosion.

Hex Bolt Grade Comparison

What Does Property Class 8.8 Mean?

For an 8.8 metric hex bolt, the designation indicates a nominal tensile-strength basis of approximately 800 MPa and a nominal yield-strength ratio of 0.8.

The corresponding nominal yield-strength basis is approximately 640 MPa.

Actual acceptance requirements must follow the applicable mechanical-property standard and bolt size.

What Does Property Class 10.9 Mean?

A 10.9 hex bolt has a nominal tensile-strength basis of approximately 1,000 MPa and a nominal yield-strength ratio of 0.9.

The corresponding nominal yield-strength basis is approximately 900 MPa.

A higher property class should not be selected solely because it is stronger. Joint ductility, fatigue loading, coating compatibility and installation procedures must also be considered.

Hex Bolt Standards

DIN 931 and DIN 933 Hex Bolts

DIN 931 hex bolts are partially threaded metric hexagon head bolts commonly used in machinery, steel structures and industrial equipment. DIN 931 is widely associated with ISO 4014, although dimensional details should be checked before treating the two standards as fully interchangeable.

DIN 933 hex bolts are fully threaded metric hexagon head bolts commonly used for general assembly, tapped holes and applications requiring a wider clamping range. DIN 933 is widely associated with ISO 4017.

DIN 931 and DIN 933 remain common terms in international purchase orders and technical drawings. When quoting these products, the required standard edition, diameter, thread pitch, bolt length, property class and coating should be confirmed.

ISO 4014 vs ISO 4017

The primary difference between ISO 4014 and ISO 4017 is the thread configuration:

ASTM F3125 Structural Bolts

The former standalone ASTM A325 and A490 specifications were consolidated into ASTM F3125/F3125M.

Current purchase descriptions should therefore use:

• ASTM F3125 Grade A325
• ASTM F3125 Grade A490
• ASTM F3125 Grade A325M
• ASTM F3125 Grade A490M

A general-purpose high-strength bolt should not automatically be substituted for a structural bolt without engineering approval.

Thread Systems

Metric Threads

Metric hex bolts can be supplied with coarse or fine threads.

Typical sizes include:

• M6
• M8
• M10
• M12
• M16
• M20
• M24
• M30
• M36
• M42
• M48
• M56
• M64

A metric fine-thread bolt should be specified using the nominal diameter and pitch, for example:

M20 × 1.5 × 100 mm

UNC and UNF Threads

UNC threads are commonly used for general-purpose inch-series fastening.

UNF threads have a finer pitch and may be selected for equipment requiring a specific thread engagement, adjustment or preload arrangement.

The purchase order should state:

• Nominal diameter
• Threads per inch
• Thread series
• Thread class
• Bolt length

A typical description is:

3/4 inch–10 UNC × 3 inches long, Class 2A external thread

Hex Bolt Dimensions

The main dimensional parameters include:

Hex bolt length is normally measured from the bearing surface under the head to the end of the bolt. The head height is not included in the nominal bolt length.

Surface Coatings

Coating Selection

The correct coating should be selected according to:

1. Bolt material and strength
2. Installation environment
3. Operating temperature
4. Chemical exposure
5. Required service life
6. Friction requirements
7. Tightening method
8. Matching nut coating

For coated bolts, the thread allowance and nut dimensions must accommodate the finished coating thickness.

Torque values for plain bolts should not automatically be applied to zinc-plated, galvanized, lubricated or fluoropolymer-coated fasteners.

Manufacturing and Quality Control

Hex bolt production may include:

1. Raw-material inspection
2. Cutting or blank preparation
3. Cold heading or hot forging
4. Thread rolling or cutting
5. Heat treatment
6. Surface preparation
7. Coating
8. Mechanical and dimensional testing
9. Marking
10. Final packing

Inspection and Testing

Available inspection items include:

• Chemical composition verification
• Tensile testing
• Yield-strength testing
• Proof-load testing
• Wedge tensile testing
• Hardness testing
• Impact testing when required
• Dimensional inspection
• Thread gauge inspection
• Coating-thickness measurement
• Positive material identification
• Visual inspection

Threads can be inspected using calibrated GO and NO-GO gauges.

For coated bolts, final thread inspection can be conducted after coating to verify compatibility with the matching nut.

Marking and Traceability

Bolt-head marking may include:

• Manufacturer identification
• Property class
• ASTM grade
• Stainless steel grade
• Production batch
• Customer-specified marking

Common markings include:

• 8.8
• 10.9
• 12.9
• A2-70
• A4-70
• A4-80
• A325
• A490
• B7

Traceability can be maintained through individual marking, bundle labels, box labels, material certificates and inspection records.

Certification and Documentation

Available documents may include:

• EN 10204 3.1 inspection certificate
• Chemical composition report
• Mechanical test report
• Proof-load test report
• Hardness report
• Heat-treatment record
• Dimensional inspection report
• Thread inspection report
• Coating certificate
• Coating-thickness report
• Positive material identification report
• Certificate of conformity
• Third-party inspection release note

Hex Bolt Applications

Our hex bolts are supplied for:

• Industrial machinery
• Structural steel construction
• Oil and gas equipment
• Petrochemical plants
• Power-generation equipment
• Pumps and valves
• Marine and offshore systems
• Shipbuilding
• Pressure equipment
• Mining machinery
• Water-treatment plants
• General fabricated assemblies

How to Order Hex Bolts

For an accurate quotation, provide the following information:

A recommended purchase description is:

HEXAGON HEAD BOLT, PARTIALLY THREADED, ISO 4014, M24 × 3.0 × 120 MM LONG, PROPERTY CLASS 8.8, HOT-DIP GALVANIZED, COMPLETE WITH COMPATIBLE HEX NUT AND FLAT WASHER, WITH EN 10204 3.1 CERTIFICATION.

Frequently Asked Questions

What is the difference between a hex bolt and a hex head screw?

Under common commercial terminology, both may be called hex bolts.

Under ISO terminology, ISO 4014 covers partially threaded hexagon head bolts, while ISO 4017 covers fully threaded hexagon head screws.

The exact standard should always be stated in the purchase order.

What is the difference between a regular hex bolt and a heavy hex bolt?

A heavy hex bolt has a larger head width and bearing surface than a regular hex bolt of the same diameter.

Heavy hex bolts are commonly used in structural and high-load industrial connections.

What is the difference between Grade 8.8 and Grade 10.9?

Grade 10.9 has a higher nominal tensile and yield-strength basis than Grade 8.8.

Grade 8.8 is widely used for general industrial equipment, while Grade 10.9 is used for more highly loaded joints. The correct grade must be selected by the equipment or structural designer.

What is the difference between A2-70 and A4-70?

A2-70 is commonly associated with 304-type stainless steel, while A4-70 is commonly associated with molybdenum-bearing 316-type stainless steel.

A4-70 generally provides better resistance in many chloride-containing and chemical environments.

Are ASTM A325 and A490 still used?

A325 and A490 remain recognized structural bolt grade designations, but they are now specified under ASTM F3125/F3125M.

Purchase orders should state ASTM F3125 Grade A325 or ASTM F3125 Grade A490.

Which coating is suitable for outdoor hex bolts?

Common outdoor coating options include:

• Hot-dip galvanizing
• Zinc-nickel
• Zinc flake
• PTFE
• Xylan

The correct coating depends on bolt strength, atmospheric exposure, temperature and required service life.

Can custom hex bolts be manufactured?

Yes. Custom diameters, lengths, thread pitches, thread lengths, head dimensions, materials, coatings and markings can be manufactured according to approved drawings.

Can hex bolts be supplied with EN 10204 3.1 certification?

Yes. EN 10204 3.1 certification can be supplied when specified at the quotation stage.

Mechanical test reports, dimensional reports, heat-treatment records and coating reports can also be provided.

Request a Hex Bolt Quotation

Send us your bill of materials, bolt schedule, drawing or project specification.

Please include:

• Dimensional standard
• Diameter and thread pitch
• Bolt length
• Full or partial threading
• Material or property class
• Surface coating
• Nut and washer requirements
• Quantity
• Certification requirements
• Inspection requirements
• Required delivery schedule

We supply ISO 4014 partially threaded hex bolts, ISO 4017 fully threaded hex bolts, ASTM A307 carbon steel bolts, ASTM A449 alloy steel bolts, ASTM F3125 structural bolts and stainless steel hex bolts with matching nuts, washers and complete inspection documentation.