ASTM F3125

Grades stocked: A325 · A490 · F1852 · F2280

Scope

ASTM F3125 / F3125M is the unified specification for high-strength, quenched-and-tempered structural bolts in two strength classes (120 ksi and 150 ksi), plus a 144 ksi class added in the 2025 revision. It consolidated and replaced six earlier standards:

• A325 and A325M (heavy hex, 120 ksi)
• A490 and A490M (heavy hex, 150 ksi)
• F1852 (twist-off, 120 ksi)
• F2280 (twist-off, 150 ksi)

F3125 went into effect in 2015. Drawings issued before that date may still cite the legacy standards — the callouts remain valid and are now published as grade designations within F3125.

Grades

Significant changes from the legacy standards

Anyone working from older drawings should know what F3125 changed:

1. Elimination of the A325 diameter "drop." Under the old A325 standard, the minimum tensile dropped from 120 ksi to 105 ksi above 1" diameter. F3125 eliminates this drop — A325 bolts 1/2" through 1-1/2" are all 120 ksi minimum tensile. Minimum pretensions published by RCSC and AISC were raised correspondingly.
2. Consolidated grade names. Old drawings specifying "A325" now call out "F3125 Grade A325." The grade designation preserves the familiar name.
3. Head markings unchanged. A325 bolts still head-mark "A325"; A490 bolts still mark "A490" to minimize field-identification disruption.
4. Grade 144 added (2025). Bridges the gap between A325 (120 ksi) and A490 (150 ksi) and is available in both heavy hex and twist-off styles, up to 1-1/4".

Mechanical properties

Grade A325 (Type 1)

• Tensile: 120 ksi min, all diameters
• Yield (0.2% offset): 92 ksi min
• Elongation in 2": 14% min
• Reduction of area: 35% min
• Proof load: 85 ksi

Grade A490 (Type 1)

• Tensile: 150 ksi min, 173 ksi max
• Yield (0.2% offset): 130 ksi min
• Elongation in 2": 14% min
• Reduction of area: 40% min
• Proof load: 120 ksi

Grade 144 (new)

• Tensile: 144 ksi min
• Yield: 117 ksi min (typical)
• Applicable to structural connection design as defined by AISC

Types

• Type 1 — Medium carbon, carbon-boron, or alloy steel. The default for most interior and non-weathering applications. Suitable for galvanizing under defined controls.
• Type 3 — Weathering steel providing atmospheric corrosion resistance similar to ASTM A242 or A588 steels. Used with weathering-steel structural members. Type 3 bolts carry a supplementary "A325" or "A490" mark plus an underline or other identifier to distinguish from Type 1.

Type 2 was removed years ago.

Approved nuts and washers

For A325, F1852 (Grade 120 ksi)

• Nuts: A563 DH (Type 1 or Type 3), A563 DH3, A563 Grade C with heavy hex when specified; A194 2H may substitute for A563 DH in Type 1
• Washers: F436 (Type 1 or Type 3 matching bolt type)

For A490, F2280 (Grade 150 ksi)

• Nuts: A563 DH or DH3 (Type matching bolt type); A194 2H may substitute for A563 DH in Type 1
• Washers: F436 (matching type); F436 is required where slotted holes, oversized holes, or turn-of-nut tensioning requires load distribution

For Grade 144

• Nuts and washers per the 2025 F3125 tables; confirm current revision before fabrication

Coatings

Grade A325 (Type 1)

• Hot-dip galvanized per F2329 — the standard coating for exterior A325
• Mechanical galvanizing per B695 — alternative
• Zinc-flake coating per F3019 or F1136 Grade 3 — engineered coating systems for longer service life

Grade A490

• Coating is restricted. Hot-dip and mechanical galvanizing are not permitted on A490 due to hydrogen embrittlement risk.
• Approved coatings are limited to F2833 Grade 1 or F1136 Grade 3 (zinc-flake systems with documented hydrogen embrittlement testing).
• Galvanized weathering-steel A490 Type 3 is also prohibited.

Grade A325 Type 3 and Grade A490 Type 3

• Weathering-steel bolts are typically furnished plain — the weathering alloy provides its own corrosion resistance. Coating is not usually applied.

Installation methods

F3125 bolts are pretensioned via one of four methods defined by the Research Council on Structural Connections (RCSC):

1. Turn-of-nut — Bring to snug tight, then rotate the specified additional turn
2. Calibrated wrench — Torque to a value calibrated per lot on a Skidmore-Wilhelm device
3. Twist-off tension control (F1852, F2280, Grade 144 TC) — Splined end shears off at a calibrated tension
4. Direct tension indicator (DTI) — F959 compressible washer; tension verified by gap measurement

Rotational capacity

F3125 requires rotational-capacity testing for galvanized assemblies — the bolt-nut-washer stack must accept the specified rotation without stripping, shearing, or failure when lubricated as supplied. Field lubricant must not be cleaned off.

Marking requirements

• Grade A325 bolts mark "A325" on the head
• Grade A490 bolts mark "A490" on the head
• Type 3 bolts add an underline under the grade mark, or the grade mark appears in a raised-border format per the standard
• Manufacturer's identification symbol appears alongside the grade
• Twist-off style marks the grade on the head; the splined end carries no mark

Galvanized A490 — the short version

Don't. F3125 prohibits it. If you need corrosion resistance on a 150 ksi bolt, specify F3125 Grade A490 Type 3 (weathering) for exterior-atmospheric service, or use an F2833 / F1136 zinc-flake coating, or step up to a stainless alternative.

Related specifications

• A563 — Carbon and alloy nuts (DH, DH3 grades pair with F3125)
• A194 — 2H heavy hex nuts (permitted substitute for A563 DH on Type 1)
• F436 — Hardened washers
• F959 — Direct tension indicators
• F2329 — HDG for Type 1 A325
• F3019 / F1136 / F2833 — Engineered zinc-flake coating systems
• RCSC Specification — Installation and inspection requirements
• AISC 360 — Steel construction specification (references F3125)

Documentation

California Fastener F3125 orders ship with mill certs showing grade, type, heat number, rotational capacity test results (for galvanized assemblies), and coating thickness reports. Project submittal packages available on request for AISC-certified fabrication.