Technically reviewed by Vincent, Founder at HEXVARO
Last reviewed · Tables updated
Sourcing these sizes? Structural bolt supplier Fastener assemblies and kitting
A325 heavy hex structural bolt dimensions (in)
Basic dimensions per ASME B18.2.6. Thread length is a reference value; it is deliberately short so that threads stay out of the shear plane in most connections.
| Diameter | Width across flats F | Head height H | Thread length | Heavy hex nut A563 — across flats | Inquiry |
|---|---|---|---|---|---|
| 1/2 | 7/8 | 5/16 | 1 | 7/8 | Quote this size |
| 5/8 | 1-1/16 | 25/64 | 1-1/4 | 1-1/16 | Quote this size |
| 3/4 | 1-1/4 | 15/32 | 1-3/8 | 1-1/4 | Quote this size |
| 7/8 | 1-7/16 | 35/64 | 1-1/2 | 1-7/16 | Quote this size |
| 1 | 1-5/8 | 39/64 | 1-3/4 | 1-5/8 | Quote this size |
| 1-1/8 | 1-13/16 | 11/16 | 2 | 1-13/16 | Quote this size |
| 1-1/4 | 2 | 25/32 | 2 | 2 | Quote this size |
| 1-3/8 | 2-3/16 | 27/32 | 2-1/4 | 2-3/16 | Quote this size |
| 1-1/2 | 2-3/8 | 15/16 | 2-1/4 | 2-3/8 | Quote this size |
Structural bolt vs ordinary hex bolt
- Head: an A325 bolt has a heavy hex head, one size larger across flats than a standard hex bolt of the same diameter. A 3/4 in A325 head is 1-1/4 in across flats; a 3/4 in hex cap screw head is 1-1/8 in.
- Thread: structural bolts have a short, fixed thread length. A 3/4 in bolt has 1-3/8 in of thread regardless of length, so most of the shank stays plain.
- Testing and marking: F3125 requires lot traceability, the grade marking (A325) and the manufacturer's mark on the head, and specific mechanical tests.
- System: the bolt, nut and washer are designed and tested as an assembly. Mixing in commercial nuts or soft washers invalidates the assembly.
A325 vs A490 (ASTM F3125)
Under the former A325 standard, bolts over 1 in had lower minimums (105 ksi tensile). F3125 raised Grade A325 to 120 ksi tensile and 92 ksi yield for all diameters, matching the values design guides already used. Type 1 is medium-carbon or alloy steel; Type 3 is weathering steel for unpainted weathering-steel structures.
| Grade | Min. tensile | Min. yield | Proof load stress | Hardness | Hot-dip galvanizing | Inquiry |
|---|---|---|---|---|---|---|
| A325 (Type 1 or 3) | 120 ksi | 92 ksi | 85 ksi | HRC 24–35 | Permitted (ASTM F2329 or mechanical galvanizing) | Quote this size |
| A490 (Type 1 or 3) | 150 ksi min, 173 ksi max | 130 ksi | 120 ksi | HRC 33–38 | Not permitted | Quote this size |
Matching nuts and washers
| Bolt | Finish | Nut | Washer | Inquiry |
|---|---|---|---|---|
| A325 Type 1 | Plain | ASTM A563 Grade C, DH (or A194 2H) | ASTM F436 Type 1 | Quote this size |
| A325 Type 1 | Hot-dip or mechanically galvanized | ASTM A563 Grade DH, galvanized and overtapped | ASTM F436 Type 1, galvanized | Quote this size |
| A325 Type 3 | Weathering | ASTM A563 Grade C3 or DH3 | ASTM F436 Type 3 | Quote this size |
| A490 | Plain | ASTM A563 Grade DH (or A194 2H) | ASTM F436 | Quote this size |
Need these ASTM F3125 Grade A325 sizes? Request a quote
- Galvanized A325 assemblies must be rotational capacity tested by the supplier as a matched lot of bolts, nuts and washers. Keep the three components together in shipping and on site.
- Nuts for galvanized bolts are lubricated; do not wash the lubricant off before installation.
Approximate weight per 100 assemblies (lb, bolt with nut)
Weights are for plain heavy hex structural bolts with one heavy hex nut, from published chart values. Use them to plan freight and site handling.
| Diameter | Length 2 in | Length 2-1/2 in | Length 3 in | Length 4 in | Inquiry |
|---|---|---|---|---|---|
| 5/8 | 37.4 | — | 46.1 | — | Quote this size |
| 3/4 | 58.4 | 64.7 | 70.9 | 83.3 | Quote this size |
| 7/8 | — | 94.6 | 103 | 120 | Quote this size |
| 1 | — | — | 141 | 162 | Quote this size |
How to specify structural bolts in your RFQ
- Grade and type: ASTM F3125 Grade A325 or A490, Type 1 or Type 3 (weathering).
- Diameter × length, and whether nuts and F436 washers are supplied as matched sets.
- Finish: plain, hot-dip galvanized (A325 only) or mechanically galvanized; state the coating standard.
- Project documents: mill certificates, lot traceability and rotational capacity test reports for galvanized assemblies.
- Quantity per size, packaging by lot, destination port and labelling for site use.
A325 compared with A307 and A490
A325 sits between the general-purpose A307 bolt and the stronger A490 bolt. Minimum tensile strength is 60 ksi for A307 Grade A, 120 ksi for A325, and 150 to 173 ksi for A490. A325 can be hot-dip galvanized, while A490 must not be.
Order these sizes from HEXVARO
Send your size list with grade, finish and quantity — we reply within 2 working hours with price, lead time and shipping terms.
- Reply: within 2 working hours
- MOQ: 500 pcs per specification
- Lead time: 10–15 days stock items
- Payment: T/T · L/C · PayPal
- Shipping ports: Tianjin · Ningbo · Shanghai · Shenzhen
- Incoterms: EXW · FOB · CFR · CIF · DAP
- Experience: Founder with 10+ years in the fastener industry
Frequently asked questions
Is A325 still a valid specification?
Yes, as a grade. ASTM withdrew the separate A325 and A490 standards in 2016 and now specifies them as grades within ASTM F3125.
What is the tensile strength of an A325 bolt?
120 ksi minimum tensile and 92 ksi minimum yield for all diameters from 1/2 to 1-1/2 in under ASTM F3125.
What wrench size is a 3/4 inch A325 bolt?
1-1/4 in. Structural bolts use heavy hex heads and heavy hex nuts, one size larger than a standard 3/4 in hex cap screw (1-1/8 in).
Can A490 bolts be galvanized?
No. Hot-dip galvanizing is not permitted for A490 because of hydrogen embrittlement risk. A325 bolts can be hot-dip or mechanically galvanized.
Do galvanized A325 bolts need rotational capacity testing?
Yes. Under F3125 galvanized assemblies must be rotational capacity tested by the responsible party, as a matched lot of bolt, nut and washer.
What is the MOQ for A325 structural bolts?
Reference MOQ is 500 pcs per specification. Stock sizes typically ship in 10–15 days and made-to-order sizes in 25–30 days, subject to quotation.
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