Aug 2025
ASTM F3125
Note: In 2016, ASTM officially withdrew specifications A325 and A490 and consolidated them under the new ASTM F3125 standard. A325 and A490 heavy hex structural bolts are now recognized as grades within ASTM F3125. The summaries of the obsolete A325 and A490 specifications are retained on our site for reference purposes only.
ASTM F3125 Specification:
This standard covers the chemical, physical, and mechanical requirements for structural bolts made from steel and alloy steel. It includes two strength grades, two styles, and two types of bolts.
ASTM F3125 replaces six older ASTM standards: A325, A325M, A490, A490M, F1852, and F2280, and applies to bolts from ½" up to 1½" diameter.
The key change is that A325 bolts sized 1-1/8" to 1-1/2" now have the same strength requirements as bolts 1? and smaller. Earlier, the larger bolts had slightly lower strength limits.
F3125 Bolt Types
| Grade |
Min Strength, Tensile |
Type |
Style |
| A325 |
120 ksi min |
1 or 3 |
Heavy Hex Head |
| A325M |
830 MPa min |
1 or 3 |
Heavy Hex Head |
| F1852 |
120 ksi min |
1 or 3 |
Twist-Off / TC |
| A490 |
150–173 ksi |
1 or 3 |
Heavy Hex Head |
| A490M |
1040 MPa |
1 or 3 |
Heavy Hex Head |
| F2280 |
150 ksi |
1 or 3 |
Twist-Off / TC |
- Type 1 – 120 ksi: Carbon, carbon boron, alloy, or alloy boron steel
- Type 1 – 150 ksi: Alloy or alloy boron steel
- Type 3 – Weathering steel
|
Chemical Requirements – Type 3
| Heat Analysis |
120 ksi, % |
150 ksi, % |
| Carbon |
0.30 – 0.52 |
0.30 – 0.48* |
| Manganese |
0.60 min. |
0.60 min. |
| Phosphorus |
0.035 max. |
0.035 max. |
| Sulfur |
0.040 max. |
0.040 max. |
| Silicon |
0.15 – 0.30 |
- |
| Boron |
0.003 max. |
0.003 max. |
| Copper |
- |
- |
| Nickel |
- |
- |
| Chromium |
- |
- |
| Molybdenum |
- |
- |
|
*Carbon 0.35–0.53% for 1-1/2” A490 / 150 ksi bolts
|
F3125 Mechanical Properties
| Grade |
Tensile, ksi |
Yield, ksi min. |
Elongation, % min. |
RA, % min. |
| 120 ksi (A325 / F1852) |
120 min. |
92 |
14 |
35 |
| 150 ksi (A490 / F2280) |
150 – 173 |
130 |
14 |
40 |
F3125 Marking Requirements & Matching Components
|
120 ksi, Type 1 |
120 ksi, Type 3 |
150 ksi, Type 1 |
150 ksi, Type 3 |
| Marking |
A325 |
A325 |
A490 |
A490 |
| Nut (Plain) |
A563 DH |
A563 DH3 |
A563 DH |
A563 DH3 |
| Nut (Coated) |
A563 DH |
A563 DH3 |
A563 DH |
A563 DH3 |
| Washer |
F436-1 |
F436-3 |
F436-1 |
F436-3 |
- A194 2H nuts may be used instead of A563 DH nuts.
- Other suitable plain finish nuts are listed in ASTM F3125.
- Special marking requirements apply under Supplementary Requirements S1 and S2.
|
F3125 Permitted Coatings
| Bolt Grade |
ASTM F2329
Hot-Dip Galvanized |
ASTM B695
Mechanical Galvanized |
ASTM F1136
Zinc/Aluminum (Geomet) |
ASTM F2833
Zinc/Aluminum |
| A325 |
Permitted |
Class 55 Approved |
Grade 3 Coating |
Grade 1 Coating |
| F1852 (TC Bolt) |
Not Permitted |
Class 55 Approved |
Not Permitted |
Not Permitted |
| A490 |
Not Permitted |
Not Permitted |
Grade 3 Approved |
Grade 1 Approved |
| F2280 (TC Bolt) |
Not Permitted |
Not Permitted |
Not Permitted |
Not Permitted |
- Other protective finishes may be applied to A325 (120 ksi) fasteners if agreed upon between supplier and purchaser.
- For A490 (150 ksi) fasteners, coatings must be tested and approved through ASTM F16 committee guidelines.
- Note: ASTM F1136, F2833, and F3019 standards were withdrawn in 2020 and consolidated into ASTM F3393 for zinc-aluminum coatings.
|
F3125 Nut Overtap Allowances
| Nominal Size |
Coating Thickness (F2329 & B695), in |
Coating Thickness (F1136 & F2833), in |
| ½-13 |
0.018 |
0.009 |
| 5/8-11 |
0.020 |
0.010 |
| ¾-10 |
0.020 |
0.010 |
| 7/8-9 |
0.022 |
0.011 |
| 1-8 |
0.024 |
0.012 |
| 1-1/8-7 |
0.024 |
0.012 |
| 1-1/4-7 |
0.024 |
0.012 |
| 1-3/8-6 |
0.027 |
0.014 |
| 1-1/2-6 |
0.027 |
0.014 |
- Hot-dip galvanized nuts are tapped after coating, while other coatings are applied after nut tapping.
- Nuts overtapped for use with 150 ksi (A490) bolts must be proof load tested to a minimum of 175 ksi after overtapping.
|
F3125 Supplemental Requirements
| S1 |
A325 (120 ksi) bolts up to 4× the diameter threaded full length. Marked as A325T. |
| S2 |
Alternate head geometry or thread length. Marked as A325S or A490S. |
| S3 |
Lubricants |
| S4 |
Rotational Capacity Testing. |