# ASTM A325

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ASTM standard

**ASTM A325** is an [ASTM International](/source/ASTM_International) standard for heavy hex structural [bolts](/source/Bolt_(fastener)), titled *Standard Specification for Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum Tensile Strength*. It defines mechanical properties for bolts that range from 1⁄2 to 1+1⁄2 inches (13 to 38 mm) in diameter.[1]

The equivalent metric standard is **ASTM A325M**, which is titled *Standard Specification for Structural Bolts, Steel, Heat Treated 830 MPa Minimum Tensile Strength*. It defines mechanical properties for sizes M12–36.[2]

This is a standard set by the standards organization [ASTM International](/source/ASTM_International), a voluntary standards development organizations that sets technical standards for materials, products, systems, and services.

In 2016, ASTM officially withdrew specification A325 and replaced it with ASTM F3125.[3] To minimize confusion, bolt head markings are unchanged and the designation A325 is retained as a grade name within the new standard.[4] In 1951, A325 bolts were recognized as equivalent to a hot driven ASTM A141 rivet.[5]

## Types

The *type* refers to the type of material used to make the bolt. The standard currently defines two types, however it previously defined the following three:[6]

- Type 1: [Medium carbon steel](/source/Medium_carbon_steel), [boron steel](/source/Boron_steel), or medium carbon [alloy steel](/source/Alloy_steel)

- Type 2: Low carbon [martensitic](/source/Martensitic) steel[7] (withdrawn from the standard in 1991)

- Type 3: [Weathering steel](/source/Weathering_steel)

There is also a *T* version, which is used to refer to fully threaded bolts.[6]

Note that independent of the material the bolt is [quenched](/source/Quench) and [tempered](/source/Tempering_(metallurgy)).[7]

## Connection types

There are also three connection types defined:[6]

- **SC**: A slip critical connection.

- **N**: A bearing type connection where the threads are on the shear plane.

- **X**: A bearing type connection where the threads are not on the shear plane.

## Mechanical properties

### Mechanical properties, imperial

These types of bolts are designed to be tightened to near their [proof strength](/source/Proof_strength), in order to create significant bolt tension. The standard states that the bolts must be tightened to at least 70% of the [tensile yield strength](/source/Tensile_yield_strength). These bolts use the same material as their common cousins ([ASTM F568M](/source/ASTM_F568M) for metric bolts), but have a thicker and wider head to more effectively distribute the load. This modified geometry is often referred to as *heavy hex* geometry.[8] Nuts must meet ASTM A563, which also uses heavy hex geometry.[9] Dimensions of heavy hex geometry are per document ANSI/ASME B18.2.6, which uses "coarse" threads as defined by [Unified Thread Standard](/source/Unified_Thread_Standard).

ASTM 325 bolts can be considered equivalent to Grade 8.8 bolts according to [ASTM F568M](/source/ASTM_F568M).[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

For a higher strength version of this type of bolt, see [ASTM A490](/source/ASTM_A490).

Head markings and mechanical properties for imperial sizes[7] Head marking Grade Nominal size range [in] Proof strength [ksi] Yield strength (min) [ksi] Tensile strength (min) [ksi] Core hardness [Rockwell][10] or[10] Type 1 1⁄2–1 (inc.) 85 92 120 C24–35 1–1+1⁄2 74 81 105 C19–31 Type 2 1⁄2–1 85 92 120 C24–35 [11] Type 3 1⁄2–1 85 92 120 C24–35 1–1+1⁄2 74 81 105 C19–31

### Mechanical properties, metric

Head markings and mechanical properties for metric sizes[8] Head marking Grade Nominal size range [mm] Proof strength [MPa] Yield strength (min) [MPa] Tensile strength (min) [MPa] Core hardness [Rockwell] Type 1 12–36[2] 600 660 830 C23–34 Type 2 Type 3

/mm

## See also

- [ASTM F568M](/source/ASTM_F568M)

## References

1. **[^](#cite_ref-1)** [*ASTM A325 - 09*](http://www.astm.org/Standards/A325.htm), retrieved 2009-06-13.

1. ^ [***a***](#cite_ref-astm_metric_2-0) [***b***](#cite_ref-astm_metric_2-1) [*ASTM A325M - 09*](http://www.astm.org/Standards/A325M.htm), retrieved 2009-06-13.

1. **[^](#cite_ref-3)** ["A325 Structural Bolts"](https://www.a325bolts.com/). Portland Bolt. Retrieved 2019-01-18.

1. **[^](#cite_ref-4)** Shaw, Robert E. Jr. (Nov 2015). ["New Twists and Turns"](https://www.structuremag.org/?p=9252). *STRUCTURE Magazine*.

1. **[^](#cite_ref-5)** [Research Council on Structural Connections](/source/Research_Council_on_Structural_Connections) (Jan 1951), [*Specifications for Assembly of Structural Joints Using High Tensile Steel Bolts*](https://www.aisc.org/products/publication/historic-standards/specifications-for-assembly-of-structural-joints-using-high-tensile-steel-bolts---january-1951/), American Institute of Steel Construction

1. ^ [***a***](#cite_ref-portland_6-0) [***b***](#cite_ref-portland_6-1) [***c***](#cite_ref-portland_6-2) ["ASTM A325 - Portland Bolt"](http://www.portlandbolt.com/technicalinformation/astm/ASTM_A325.html). Retrieved 2009-06-13..

1. ^ [***a***](#cite_ref-american_7-0) [***b***](#cite_ref-american_7-1) [***c***](#cite_ref-american_7-2) [*ASTM, SAE and ISO grade markings and mechanical properties for steel fasteners*](http://www.americanfastener.com/technical/grade_markings_steel.asp), retrieved 2009-06-06.

1. ^ [***a***](#cite_ref-uiowa_8-0) [***b***](#cite_ref-uiowa_8-1) ["Metric structural fasteners"](https://web.archive.org/web/19990421064802/http://www.icaen.uiowa.edu/%7Esdesign1/Text/fasteners_si.html). University of Iowa. Archived from [the original](http://www.icaen.uiowa.edu/~sdesign1/Text/fasteners_si.html) on 1999-04-21. Retrieved 2009-06-06..

1. **[^](#cite_ref-9)** Kulak, Geoffrey L. (2001). [*Guide to Design Criteria for Bolted and Riveted Joints*](http://www.boltcouncil.org/files/2ndEditionGuide.pdf) (PDF) (2nd ed.). American Institute of Steel Construction. p. 37. [ISBN](/source/ISBN_(identifier)) [978-1564240750](https://en.wikipedia.org/wiki/Special:BookSources/978-1564240750).

1. ^ [***a***](#cite_ref-fastspec_10-0) [***b***](#cite_ref-fastspec_10-1) [*Grade Markings: Carbon Steel Bolts*](http://www.fastspecinc.com/technical/technical.html), retrieved 2009-05-30.

1. **[^](#cite_ref-crnote_11-0)** Other markings may be used to denote atmospheric corrosion resistant material

v t e ASTM Standards Selected standards A ASTM A53 ASTM A325 ASTM A354 ASTM A490 ASTM A500 ASTM A992 C ASTM C131 ASTM C535 D ASTM D5800 E ASTM E1714 F ASTM F568M ASTM F883 Related ASTM International Award of Merit Charles Benjamin Dudley ASTM Subcommittee E20.02 on Radiation Thermometry

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Adapted from the Wikipedia article [ASTM A325](https://en.wikipedia.org/wiki/ASTM_A325) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/ASTM_A325?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.