ASTM F3125 A490 structural bolts are quenched-and-tempered alloy-steel fasteners for high-strength structural connections. The current ASTM F3125/F3125M-26 specification retains Grade A490 as the inch-series heavy hex style with a minimum tensile strength of 150 ksi. Heavy hex Grade A490 bolts are furnished from 1/2 through 1-1/2 inches and use Unified National Coarse threads. Typical assemblies combine the bolt with a compatible heavy hex nut and hardened structural washer selected for Type 1 or Type 3 service. Buyers commonly specify these assemblies for steel buildings, bridges, industrial structures, towers, and other engineered joints requiring the higher A490 strength level.
Product Overview and Key Features
Grade A490 is the higher-strength heavy hex grade in the traditional A325/A490 family. The former standalone ASTM A490 specification was consolidated into ASTM F3125, so current orders should identify F3125 Grade A490.
- 150 ksi strength grade: 150 ksi minimum tensile, 173 ksi maximum tensile, and 130 ksi minimum yield strength.
- Heavy hex geometry: dimensions follow the structural fastener geometry referenced by ASTM F3125 and ASME B18.2.6.
- UNC Class 2A threads: standard inch-series bolts use Unified National Coarse threads.
- Type 1 and Type 3: alloy-steel and weathering-steel material routes are available within the grade.
- Matched assembly selection: coordinate the bolt, nut, washer, coating, lubrication, and installation requirements.
ASTM F3125 A490 Structural Bolts Specifications
Specification Overview
| Item | Specification |
|---|---|
| Current standard | ASTM F3125/F3125M-26 |
| Grade and style | Grade A490, Heavy Hex |
| Nominal diameter range | 1/2 in. through 1-1/2 in. |
| Thread series | UNC, Class 2A |
| Tensile strength | 150 ksi minimum, 173 ksi maximum |
| Minimum yield strength | 130 ksi |
| Material types | Type 1 and Type 3 |
| Common matching nuts | ASTM A563 DH for Type 1; A563 DH3 for Type 3 |
| Common matching washers | ASTM F436 Type 1 for Type 1; F436 Type 3 for Type 3 |
Dimensions and Thread Details
This selection shows seven common diameters. TPI means threads per inch, F is width across flats, H is head height, and T is basic thread length. Example lengths are catalog combinations, not an ASTM continuous supply range or Flybear inventory statement.
| Nominal Thread | UNC TPI | Example Length (in.) | F Basic (in.) | H Min-Max (in.) | T Basic (in.) |
|---|---|---|---|---|---|
| 3/4-10 | 10 | 2 | 1-1/4 | 0.455-0.483 | 1.38 |
| 7/8-9 | 9 | 2-1/2 | 1-7/16 | 0.531-0.563 | 1.50 |
| 1-8 | 8 | 3 | 1-5/8 | 0.591-0.627 | 1.75 |
| 1-1/8-7 | 7 | 3-1/2 | 1-13/16 | 0.658-0.718 | 2.00 |
| 1-1/4-7 | 7 | 4 | 2 | 0.749-0.813 | 2.00 |
| 1-3/8-6 | 6 | 4-1/2 | 2-3/16 | 0.810-0.878 | 2.25 |
| 1-1/2-6 | 6 | 5 | 2-3/8 | 0.902-0.974 | 2.25 |
The scope also includes 1/2-13 and 5/8-11 Grade A490 heavy hex bolts. Standard structural bolts use controlled partial-thread geometry. Nonstandard dimensions should be ordered under the applicable supplementary requirements.
Common Materials, Grades and Surface Finishes
Material and Grade Options
Grade A490 Type 1 uses qualifying alloy steel or alloy steel with boron addition and is quenched and tempered to achieve the specified properties. Type 3 uses weathering-steel chemistry for atmospheric corrosion resistance and should be paired with compatible Type 3 hardware. Type 3 is a material system, not simply a surface finish.
Coating and Finish Options
Plain finish is common. For corrosion-protected 150 ksi A490 assemblies, ASTM F3125 provides for qualified ASTM F3393 zinc-flake coating systems. ASTM F2329 hot-dip galvanizing and ASTM B695 mechanical zinc are not the specified coating routes for Grade A490 150 ksi bolts. Coated assemblies require compatible nut thread accommodation, lubrication, and proof-load control. Confirm the complete finish and mating-hardware combination during quotation.
Typical Applications and Selection Considerations
- Beam, column, splice, and bracing connections in structural steel frames.
- Bridge, gantry, platform, and heavy infrastructure connections.
- Towers, substations, utility structures, and industrial support steelwork.
- Joints where the structural design specifies the higher Grade A490 strength level.
Flybear’s steel construction fastening solutions provide related sourcing context. Select diameter and length from the design and grip, then match the nut, washer, surface condition, and installation method. A490N, A490X, and slip-critical terminology describes joint design or thread location in the shear plane, not a different manufacturing grade.
Ordering and Quality Documentation
An RFQ should state ASTM F3125/F3125M Grade A490, Type 1 or Type 3, diameter-TPI, length, finish, quantity, nut grade, washer type, and documentation requirements. Buyers may request material records, dimensional checks, thread gauging, mechanical test records, coating verification, and lot traceability. Flybear’s quality control and inspection page describes available inspection support; exact requirements should be agreed for the order.
Frequently Asked Questions
Is ASTM A490 still a standalone current standard?
No. ASTM A490 was consolidated into ASTM F3125. Current purchasing language should use ASTM F3125 Grade A490, although older drawings and trade terminology often continue to say “A490.” The designation now identifies the 150 ksi heavy hex structural grade within F3125.
How is Grade A490 different from Grade A325?
Both are heavy hex structural grades under ASTM F3125, but A490 has a 150 ksi minimum tensile strength while A325 is the 120 ksi grade. Their coating provisions also differ, so an A325 finish specification should not automatically be applied to A490.
What nuts and washers are commonly paired with A490 bolts?
Type 1 commonly pairs with ASTM A563 DH heavy hex nuts and ASTM F436 Type 1 washers. Type 3 commonly pairs with A563 DH3 nuts and F436 Type 3 washers. ASTM A194 Grade 2H heavy hex nuts are also recognized for certain Type 1 configurations.
Can A490 bolts be hot-dip galvanized?
ASTM F3125 does not use ASTM F2329 hot-dip galvanizing for 150 ksi Grade A490 assemblies. Where corrosion-protected A490 fasteners are required, qualified ASTM F3393 zinc-flake systems are the relevant route. Specify the coated assembly with compatible nuts and lubrication.
What should an A490 RFQ include?
State ASTM F3125 Grade A490, Type 1 or Type 3, diameter, TPI, length, quantity, finish, nut and washer requirements, and documentation. Include drawings or a bill of materials when grip, joint geometry, special dimensions, or project coating requirements affect selection.
Request a Quote for ASTM F3125 A490 Structural Bolts
Send Flybear Industrial your Grade A490 type, diameter, length, finish, quantity, nut grade, washer requirement, and documentation needs. Include drawings when connection details control selection. Submit the project through the Flybear fastener RFQ page for review and quotation.
