ASTM F3125: A325, A490, F1852 and F2280 in one standard
ASTM F3125 is the single standard for high-strength structural bolts. It consolidated and replaced six earlier standards: A325, A325M, A490, A490M, F1852 and F2280. The grade names were kept, so an A325 bolt is now an ASTM F3125 Grade A325 bolt with 120 ksi minimum tensile strength.
Contents9 sections
Key takeaways
- F3125 replaced A325, A325M, A490, A490M, F1852 and F2280, and added a 144 ksi grade (inch only) 1.
- Grade A325 and F1852 are 120 ksi minimum; A490 and F2280 are 150 ksi minimum and 173 ksi maximum 2 3.
- Heavy hex A325/A490 come in 1/2 to 1-1/2 in; twist-off F1852/F2280 in 1/2 to 1-1/4 in 1.
- A325 is now 120 ksi at every size; the old A325 dropped to 105 ksi above 1 in 2 4.
Quick facts
| Current edition | F3125/F3125M-26 (Active) |
|---|---|
| Inch grades | A325, A490, F1852, F2280, 144 |
| Metric grades | A325M, A490M, M12 to M36 |
| Types | Type 1 and Type 3 (weathering) |
ASTM F3125 grades
| Grade | Style | RCSC group | Min. tensile | Sizes |
|---|---|---|---|---|
| A325 | heavy hex | Group 120 | 120 ksi | 1/2-1-1/2 in |
| F1852 | twist-off (tension control) matched assembly | Group 120 | 120 ksi | 1/2-1-1/4 in |
| A490 | heavy hex | Group 150 | 150 ksi | 1/2-1-1/2 in |
| F2280 | twist-off matched assembly | Group 150 | 150 ksi | 1/2-1-1/4 in |
Consolidates and replaces A325, A325M, A490, A490M, F1852 and F2280. A325/A490 heavy hex 1/2 to 1-1/2 in.; F1852/F2280 twist-off 1/2 to 1-1/4 in.; also 144 ksi grade (inch only).12
What F3125 consolidated
ASTM F3125 “was originally issued as a consolidation and replacement of six structural bolting ASTM standards, including; A325, A325M, A490, A490M, F1852 and F2280” 1. It also added one grade, 144 ksi, in inch sizes only 1. The first edition was F3125-15. The version list then runs through 2018, 2019, 2021, 2022, 2023 and 2025 revisions to F3125/F3125M-26, the active edition when checked 1.
The old designations survive as grade names inside F3125. Drawings that still say “A325” or “A490” mean the same bolts; RCSC 2020 refers to them as ASTM F3125 Grade A325 and Grade A490 3.
The standard covers quenched and tempered steel and alloy steel bolts in inch and metric sizes. Bolts are designated by grade (strength and style) and by type (chemical composition) 1. They are intended for structural connections under the RCSC Specification 1.
Grades and sizes
| Grade | Style | Sizes | RCSC group |
|---|---|---|---|
| A325 | Heavy hex | 1/2 to 1-1/2 in | Group 120 |
| A490 | Heavy hex | 1/2 to 1-1/2 in | Group 150 |
| F1852 | Twist-off | 1/2 to 1-1/4 in | Group 120 |
| F2280 | Twist-off | 1/2 to 1-1/4 in | Group 150 |
| 144 | Twist-off and heavy hex | 1/2 to 1-1/4 in | (RCSC uses F3148 Grade 144) |
| A325M, A490M | Heavy hex | M12 to M36 | — |
Scroll the table sideways to see every column.
Sizes are from the F3125 scope (1.2.2 to 1.2.5) 1 and groups from RCSC Table 2.1 3. RCSC’s Group 144 lists only ASTM F3148 Grade 144 fixed-spline assemblies, not an F3125 grade 3.
Strength
From F3125-15 Table 4 as reproduced by St. Louis Screw & Bolt 2:
- A325 and F1852: 120 ksi minimum tensile. Proof load stress 85 ksi by the length-measurement method, 92 ksi by the yield-strength method.
- A490 and F2280: 150 ksi minimum and 173 ksi maximum tensile. Proof 120 ksi (length measurement) or 130 ksi (yield).
Full-size loads follow from the stress area. A 3/4 in A325 must reach 40,100 lbf tensile; the same A490 must reach 50,100 lbf and may not exceed 57,800 lbf. At 1-1/2 in the A325 minimum is 168,600 lbf 2.
The single strength level is the main change for A325. Under the old A325, the 2005 Fastenal guide lists 120 ksi up to 1 in and 105 ksi over 1 in to 1-1/2 in 4. Under F3125 it is 120 ksi to 1-1/2 in 2 3. That is why RCSC 2020 lists “revised values for pre-installation verification testing and for pretension for Group 120 bolts larger than 1 in.” among its changes 3. A 1-1/4 in A325 pretension is now 81 kips (360 kN) 3.
The 173 ksi cap on A490 is deliberate. Steel at 200 ksi and above is subject to hydrogen embrittlement, and the cap plus a 38 HRC maximum hardness keep a margin below that range 3.
Types
- Type 1: medium carbon, carbon boron, alloy, or alloy with boron steel 3.
- Type 3: improved atmospheric corrosion resistance and weathering characteristics 3.
When the type is not specified, the manufacturer may supply either 3. Washers and DTIs must match the bolt type, e.g. F959 Type 325-3 DTIs with Type 3 Group 120 bolts 3.
Markings
ASTM requires structural bolts, nuts and washers to carry distinctive marks; manufacturers may add their own 3. RCSC Figure C-2.1 shows the required marks 3:
- The grade designation on the head: A325, A490, F1852 or F2280, with the manufacturer’s identification mark (shown as “XYZ” in the figure). The Type 1 and Type 3 versions are drawn separately.
- F1852 and F2280 twist-off assemblies may also be made with heavy hex heads and carry similar marks.
- A325 bolts made fully threaded under the supplementary requirement (length up to four diameters) are marked T. Bolts with special thread lengths are marked S 3.
RCSC shows the Type 1/Type 3 differences only as drawings, so this page does not describe them. Check the head against Figure C-2.1 in the RCSC Specification.
Matching components
F3125 bolts are used with ASTM A563 heavy hex nuts (Grade DH for coated bolts; C, C3, D, DH or DH3 for plain Type 1 A325) and F436 washers, all dimensioned to ASME B18.2.6 3. Bolt heads and nuts have the same width across flats, so one socket fits both: 1-1/4 in for a 3/4 in bolt 3. For installation see A325 bolt torque and A490 bolt torque.
Sources
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Related
- A325A325 bolts have no RCSC torque value. Minimum pretension is 28 kips for 3/4 in and 51 kips for 1 in; the torque is found daily on the job for each wrench.
- A490A490 bolts have no RCSC torque value. Minimum pretension is 35 kips for 3/4 in and 64 kips for 1 in; RCSC bans galvanizing and reuse of A490 heavy hex bolts.
- vs Grade 5 / 8A325 matches Grade 5 strength only up to 1 in, and A490 matches Grade 8 minimums. Heavy hex heads, shorter threads and RCSC rules keep them out of each other's joints.
- Grade 8Grade 8 bolt torque from 1/4 in to 1 in, dry, zinc-plated and lubricated, with SAE J429 proof, yield and tensile strength and the six-line head marking.
- Socket size chartSocket sizes for inch hex cap screws, heavy hex structural bolts and metric bolts, including M10, M12, M14 and M22, where ISO and DIN heads differ.