ASTM A307 Bolts Supplier
MT.BOLTS manufactures ASTM A307 carbon steel bolts using high-quality low-carbon steel materials. These bolts offer reliable tensile strength, good ductility, and excellent performance in general-purpose applications where high strength alloy bolts are not required. They are ideal for use in construction, pressure piping, flanged joints, structural assemblies, and general mechanical fastening.
Our ASTM A307 bolts are available in the following specifications:
- Grades: A, B
- Diameter: M6 to M100 | 1/4″ to 4″
- Length: 10mm to 1000mm | 0.5″ to 40″
- Thread Type: Metric (Coarse/Fine) | UNC/UNF
- Head Types: Hex Head, Heavy Hex Head, Studs, Threaded Rods
- Standards: ASME B18.2.1 (Bolts), ASME B18.2.2 (Nuts), ASME B18.31.3 (Threaded Rods)
- Material Specification: ASTM A307 (Grades A & B)
- Finish Options: Plain, Zinc-Plated, Hot-Dip Galvanized, or as specified
ASTM A307 Bolts – Grades, Composition & Properties
| Grade | Description |
| A | Bolts, studs, and threaded rods with a minimum tensile strength of 60 ksi, intended for general-purpose applications. |
| B | Bolts, studs, and threaded rods with a tensile strength of 60–100 ksi, intended for flanged joints in piping systems with cast iron flanges. |
| C | Replaced by ASTM F1554 Grade 36 (mainly used for structural anchor bolts). |
Chemical Requirements for Grades A and B Bolts, Studs, and Threaded Rod
| Element | Heat Analysis (max) | Product Analysis (max) | Remarks |
| Carbon | 0.29 | 0.33 | |
| Manganese | 1.2 | 1.25 | |
| Phosphorus | 0.04 | 0.041 | |
| Sulfur | |||
| – Grade A | 0.15 | A | Resulfurized steel is not subject to rejection based on product analysis for sulfur. |
| – Grade B | 0.05 | 0.051 |
ASTM A307 Bolts – Mechanical Properties (Typical)
Hardness Requirements for Bolts, Studs, and Threaded Rod
| Grade | Length, in. | Brinell Hardness (min) | Brinell Hardness (max) | Rockwell B (min) | Rockwell B (max) |
| A | Less than 3 × dia (B) | 121 | 241 | 69 | 100 |
| 3 × dia and longer | — | 241 | — | 100 | |
| B | Less than 3 × dia (B) | 121 | 212 | 69 | 95 |
| 3 × dia and longer | — | 212 | — | 95 |
Notes:
A – Measured anywhere on the surface or through the cross section.
B – Also applies to bolts with drilled or undersize heads; these must still meet the hardness requirements.
Tensile Requirements for Full-Size Bolts, Studs, and Threaded Rod
| Bolt Size, in. | Threads per in. | Stress Area (in²) | Tensile Strength (lbf) – Grade A (min) | Tensile Strength (lbf) – Grade B (min) | Tensile Strength (lbf) – Grade B (max) |
| ¼ | 20 | 0.0318 | 1 900 | 3 180 | — |
| ⁵⁄₁₆ | 18 | 0.0524 | 3 100 | 5 240 | — |
| ⅜ | 16 | 0.0775 | 4 600 | 7 750 | — |
| ⁷⁄₁₆ | 14 | 0.1063 | 6 350 | 10 630 | — |
| ½ | 13 | 0.1419 | 8 500 | 14 190 | — |
| ⁵⁄₈ | 11 | 0.226 | 13 550 | 22 600 | — |
| ¾ | 10 | 0.334 | 20 050 | 33 400 | — |
| ⅞ | 9 | 0.462 | 27 700 | 46 200 | — |
| 1 | 8 | 0.606 | 36 350 | 60 600 | — |
| 1 ⅛ | 7 | 0.763 | 45 600 | 76 000 | — |
| 1 ¼ | 7 | 0.969 | 58 000 | 97 000 | — |
| 1 ⅜ | 6 | 1.155 | 69 300 | 115 500 | — |
| 1 ½ | 6 | 1.405 | 84 300 | 140 500 | — |
| 1 ¾ | 5 | 1.9 | 114 000 | 190 000 | — |
| 2 | 4 ½ | 2.5 | 150 000 | 250 000 | — |
| 2 ¼ | 4 ½ | 3.5 | 195 000 | 325 000 | — |
| 2 ½ | 4 | 4 | 240 000 | 400 000 | — |
| 2 ¾ | 4 | 4.93 | 295 000 | 492 000 | — |
| 3 | 4 | 5.97 | 358 000 | 597 000 | — |
| 3 ¼ | 4 | 7.03 | 426 000 | 709 000 | — |
| 3 ½ | 4 | 8.33 | 499 800 | 833 000 | — |
| 3 ¾ | 4 | 9.66 | 579 600 | 966 000 | — |
| 4 | 4 | 11.08 | 664 800 | 1 108 000 | — |
Notes:
A – Stress area Aₛ = 0.7854 × (D – 0.9743 / n)²
B – 1 lbf = 4.448 N
C – Grade A based on 60 ksi (414 MPa)
D – Grade B based on 60–100 ksi (414–690 MPa)
Tensile Requirements for Machined Specimens
| Property | Grade A | Grade B |
| Tensile strength, ksi | 60 min | 60–100 |
| Yield point, min ksi | — | — |
| Elongation in 2 in., min % | 18 | 18 |
Why Choose MT.BOLTS
- Material Diversity
- Standardized Production
- Ample Inventory
- Competitive Pricing
- Low-MOQ Customization
ASTM A307 – Standard Specification for Carbon Steel Bolts and Studs, 60,000 PSI Tensile Strength
This specification covers the chemical and mechanical requirements for carbon steel bolts and studs in sizes 1/4 inch through 4 inch.
ASTM A307 does not cover machine screws, thread-cutting/forming screws, mechanical expansion anchors, or other similar externally threaded fasteners.
Suitable Nuts (Reference ASTM A563)
| Bolt Grade & Size | Nut Grade & Style |
| A 1/4 – 1 1/2 in. | Grade A, Hex Nut |
| A over 1 1/2 – 4 in. | Grade A, Heavy Hex Nut |
| B 1/4 – 4 in. | Grade A, Heavy Hex Nut |
Note: Nuts of other grades and styles with specified proof load stresses greater than the specified grade and style are also suitable.
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Ordering Information
When ordering externally threaded fasteners under ASTM A307 (including nuts and accessories), the following information should be included:
ASTM Standard and Year
Clearly specify ASTM A307 and the year of issue.
Product Name and Type
Bolts, studs, or threaded rods.
Bolt head style: Hex or Heavy Hex.
Grade
A or B. If no grade is specified, Grade A shall be furnished by default.
Quantity
Number of pieces by size, including nuts.
Size and Length
Diameter and length of the fasteners.
Washers
Quantity and size, listed separately from the bolts.
Zinc Coating
Specify the required zinc-coating process, such as Hot-Dip, Mechanically Deposited, or no preference.
Other Finishes
Specify other protective finishes if required.
Inspection at Point of Manufacture
Indicate if inspection at the manufacturing site is required.
Certified Test Report
Specify if a certified test report is required (see 8.2).
Additional Testing or Special Requirements
Specify any additional testing (see 8.3) or special requirements if needed.
Part Identification System
For establishing a part identification system, refer to ASME B18.24.
Packaging and Package Marking
Unless otherwise specified, packaging shall follow the manufacturer’s practice to prevent damage during transportation. Any special packaging requirements should be specified at the time of inquiry or order. Each shipping unit shall be clearly marked with the ASTM designation and grade, size, manufacturer name and brand/trademark, quantity, purchase order number (if specified in the order), and country of origin.
FAQ About ASTM A307 Bolts
ASTM A307 is a standard specification covering carbon steel bolts, studs, and threaded rods with sizes from 1/4″ to 4″, classified into Grades A, B, and C (C has been replaced by ASTM F1554 Gr.36).
- Grade A: Minimum tensile strength 60 ksi, for general-purpose applications.
- Grade B: Tensile strength 60–100 ksi, used for flanged joints in piping with cast iron flanges.
- Grade C: Replaced by ASTM F1554 Gr.36, mainly for structural anchor bolts.
Hex bolts, heavy hex bolts, studs, and threaded rods. Grade A bolts are typically hex; Grade B bolts are heavy hex.
Sizes: 1/4″ to 4″ (diameter)
Threads: Coarse thread series (ASME B1.1) for bolts and studs; threaded rods follow ASME B18.31.3
Carbon steel produced by open-hearth, basic-oxygen, or electric-furnace processes.
Yes, zinc coatings can be hot-dip or mechanically deposited. Other protective finishes can also be applied per order.
Bolts and studs undergo hardness and tensile testing. Full-size testing is preferred; machined specimens are used when full-size testing is impractical.
Refer to ASTM A563. Grade A bolts: hex or heavy hex nuts; Grade B bolts: heavy hex nuts. Other nuts with sufficient proof load are also acceptable.
Bolts are marked with grade, manufacturer identifier, and optionally other information. Packaging prevents damage during transport, and each unit should indicate ASTM designation, grade, size, quantity, manufacturer, purchase order number, and country of origin.
General construction, flanged pipe joints, machinery assembly, and other structural and mechanical applications requiring carbon steel fasteners.
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