ASTM F3125 Grade A325 Type 1 Structural Bolts
Heavy hex structural bolts per ASTM F3125 Grade A325 Type 1 — medium carbon steel, quenched and tempered, 120,000 psi minimum tensile through 1 inch (105,000 psi over). The standard structural bolt for bridges, buildings and heavy construction, and the A325 type that accepts hot-dip galvanizing.
Last updated: 2026-11
Specifications
Type 1 is the default A325: a heavy hex structural bolt made of medium carbon steel (the type also covers carbon-boron and medium-carbon alloy steel), with a flat washer-faced bearing surface and a chamfered point. Heat treatment is a quench from above the austenitizing temperature followed by tempering at 800 °F or more. Its strength is size-dependent — 120,000 psi minimum tensile through 1 inch diameter, dropping to 105,000 psi above — which is why large-diameter structural joints check the mechanicals per size rather than quoting one number. One practical distinction drives type selection: Type 1 is the A325 type that can be galvanized, so coated structural work (bridges, highway structures) specifies Type 1 with a compatible nut and washer set, while uncoated weathering-steel joints go to Type 3.
| Standard | ASTM F3125 Grade A325 Type 1 — heavy hex structural bolt, washer faced, chamfered point |
|---|---|
| Material | Medium carbon steel (type also covers carbon-boron and medium-carbon alloy steel) |
| Tensile strength, min | 120,000 psi (≤ 1 in dia); 105,000 psi (> 1 in dia) |
| Yield strength, min | 92,000 psi (1/2"–1"); 81,000 psi (1-1/8"–1-1/2") |
| Proof load | 85,000 psi (1/2"–1"); 74,000 psi (1-1/8"–1-1/2") |
| Hardness | Rockwell C24–35 (1/2"–1"); C19–31 (1-1/8"–1-1/2") |
| Heat treatment | Quenched in a liquid medium from above the austenitizing temperature, tempered ≥ 800 °F |
| Finishes | Plain, zinc plate, or hot-dip galvanized — Type 1 is the A325 type that can be galvanized |
| Typical applications | Structural steel joints in bridges, highway construction and heavy construction |
Where this grade fits
A325 structural bolts are pre-tensioned, so the tightening method is part of the specification: turn-of-nut, calibrated wrench, TC bolts or DTI washers per RCSC practice, each with its own verification discipline. Type 1 is the A325 type that accepts hot-dip galvanizing — pair it with a compatible coated heavy hex nut (A563 DH or A194 2H).
Deep read: How to Determine Tightening Torque and Choose a Tightening Method for a Bolted Joint · Calculating Bolt Preload and Clamp Force: Torque, Friction and Tightening Method
Materials
- Medium carbon steel (quenched and tempered)
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (ASTM F3125 Grade A325 Type 1 Structural Bolts) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 1,000–10,000 pieces depending on size. Stock items run 3–7 days. High-strength and custom parts run 15–25 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
When is A325 Type 1 specified instead of Type 3?
By coating and environment. Type 1 is the medium-carbon-steel type and the only A325 type that can be hot-dip galvanized, so any coated structural joint — and most painted work — calls out Type 1 with galvanized heavy hex nuts and F436 washers. Type 3 is the weathering-steel type for uncoated joints that form their own patina. If the structure is weathering steel (ASTM A588), the joint normally takes Type 3; if it is ordinary structural steel with a coating system, Type 1.
What is the MOQ and lead time for this bolt grade?
The minimum order quantity is 1,000–10,000 pieces depending on size. Stock items ship in 3–7 days; high-strength and custom parts in 15–25 days. Common diameters in this grade are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
What should an RFQ for this bolt grade state?
State the standard and grade (for example ISO 4017 Class 8.8 or ASTM F3125 Grade A325 Type 1), diameter and length, thread type (metric coarse or UNC/UNF), finish (plain, zinc, or hot-dip galvanized where the grade permits), required certificates such as a mill test report per EN 10204 3.1, and quantity per size — plus destination country.
Related knowledge
- What Bolt Property Classes 8.8, 10.9 and 12.9 Encode — and When High Strength Stops Being the Right Choice
- Bolt Grade Selection: ISO 898-1 8.8/10.9/12.9 vs ASTM A307 and A325
- 8.8 vs 10.9 vs 12.9 Bolts: Strength, Hardness and Cost — What the Evidence Settles
- Calculating Bolt Preload and Clamp Force: Torque, Friction and Tightening Method
- How to Determine Tightening Torque and Choose a Tightening Method for a Bolted Joint
- Fastener Failure Modes: Which Fatigue, Creep and SCC Controls the Evidence Supports
- Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ
- Bolt Head Markings: What the Lines, Numbers and Letters Claim — and How to Verify the Grade Before Accepting a Lot
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support