Structural Bolts

Portland Bolt manufactures A325 and A490 heavy hex structural bolts from ½″ to 1½″ diameter, often producing longer bolts than those typically available off the shelf.

Stock sizes include:

• • Grade: F3125 Grade A325 Type 1
  • Diameters: ½″ – 1″
  • Lengths: Up to 5″
  • Finish: Plain or hot-dip galvanized

• Origin: Domestic manufacturing

Both Type 1 and Type 3 are classifications within the ASTM F3125 specification:

• Type 1 structural bolts are made from medium carbon or alloy steel and require a protective coating – such as galvanizing – to resist corrosion.
• Type 3 structural bolts are made from weathering steel, which naturally forms a protective rust-like patina over time, eliminating the need for paint or coating. This weathered layer seals the bolt surface and prevents deeper corrosion.

You can distinguish the two by head markings: Type 3 bolts feature an underlined grade mark, while Type 1 bolts do not.

Type 3 structural bolts are ideal for outdoor applications where the steel experiences alternating wet and dry conditions, such as in the Midwest. They are frequently used in parks, playgrounds, fences, gates, and agricultural structures where the rusted finish provides both protection and a natural aesthetic.

Type 1 hot-dip galvanized bolts are preferred in coastal or continuously damp environments—such as the Pacific Northwest or marine locations—where weathering steel cannot form a stable protective patina and would instead corrode.

• Type 1 (Grades A325 and F1852):
  • Hot-dip galvanized (ASTM F2329)
  • Mechanically galvanized (ASTM B695)
• Type 1 (Grades A490 and F2280):
  • Zinc/aluminum corrosion-protective coatings (ASTM F3393)
  • This includes combinations of ASTM F1136 Grade 3, ASTM F2833 Grade 1, and ASTM F3019 Grade 4 coatings.
  • These coatings may also be applied to A325 and F1852 bolts for additional protection.

Type 3 bolts are typically supplied plain (uncoated) since their weathering properties provide inherent corrosion resistance.

Compatibility depends on the bolt grade and type:

• • A490 Type 1 / F2280 TC bolts: A563-DH or A194-2H nuts and F436 Type 1 washers
  • A325 Type 1 / F1852 TC bolts: A563-DH, A194-2H, or A563-C (for plain finish) nuts and F436 Type 1 washers
  • A490 Type 3 bolts: A563-DH3 nuts and F436 Type 3 washers

• A325 Type 3 bolts: A563-DH3 or A563-C3 nuts and F436 Type 3 washers

Identification markings:

• • Nuts are marked per ASTM A563 (e.g., “DH” for Type 1, “DH3” for Type 3).
• Washers are marked per ASTM F436 with a manufacturer’s ID and a “3” for Type 3 weathering steel washers.

These letters identify the type of structural connection, not the bolt itself.

• SC – Slip-Critical Connection (bolt tension resists slip)
• N – Bearing-Type Connection with threads included in the shear plane
• X – Bearing-Type Connection with threads excluded from the shear plane

All three use the same A325 heavy hex structural bolt; the designation simply reflects how the bolt will function within the joint.

• A325: Medium carbon or carbon-boron steel, used for standard-strength structural connections.

A490: Alloy steel, heat-treated for higher tensile strength and load capacity.
Both are covered under ASTM F3125, but A490 bolts are stronger and require more stringent handling and coating requirements.

• A325 Type 1 & Type 3: Common and mass-produced in diameters ½″ – 1¼″

• A490 Type 1 & Type 3: Common in diameters ⅝″ – 1¼″

Longer or nonstandard lengths, custom thread lengths, or altered head dimensions can be custom manufactured by Portland Bolt.

Tension control bolts (Grades F1852 and F2280) are also widely available in these sizes but are not custom-manufactured.

• T: Fully threaded bolt (limited to 4× the diameter in length)

• M: Metric version of A325

• S: Modified thread length or head dimensions (denoting a nonstandard configuration allowed under ASTM F3125)

Under ASTM F3125, an “S” marking indicates the bolt has altered geometry that still complies with the specification.

According to ASME B18.2.6, structural bolts such as A325 and A490 can be manufactured 0.12″ to 0.25″ shorter than their nominal published length and still meet specification requirements.

This variance is common in mass production and has no effect on performance, but should be considered when selecting bolt lengths to ensure sufficient thread engagement per RCSC Specification Section 2.3.2 and AISC Table 7-14.

Yes. Portland Bolt can produce custom lengths, thread configurations, and head dimensions for structural bolts that are not available through standard suppliers. Custom tooling and domestic manufacturing ensure full compliance with ASTM and ASME specifications while accommodating project-specific requirements.