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Comparison of ASTM A325 and A449

I have two items that use 1″ bolts, one is ASTM A325 and the other is ASTM A449, I would like to just use one. Which is the one that meets or exceeds the other?

These bolts are identical with regard to strength and chemistry. There are very minor differences in the hardness requirements, but the proof load, tensile, and yield strength requirements are the same. From a manufacturing standpoint, we make these bolts using the same raw material and the same heat treating and production methods. Our strength by grade chart gives a detailed comparison.

The difference between these two specifications (A325 and A449) is the diameter range, configuration, and application. A325 bolts are heavy hex head bolts ONLY, and are designed for structural steel connections. They range in diameter from ½” – 1-1/2” inclusive. Due to their application, an A325 structural bolt has a shorter thread length than a typical heavy hex bolt. If you need a bolt with longer threads, ASTM A449 should be used.

ASTM A449 bolts range in diameter from ¼” – 3” inclusive and are far more flexible in their configuration. In other words, A449 bolts can be a headed bolt, a straight rod with threads, or a bend bolt such as a right angle bend foundation bolt.

With regard to availability, A325 bolts are mass produced and far more common in the marketplace than A449 bolts. Therefore, A325 bolts would be immediately available and considerably less expensive than A449 bolts, unless the bolts you are dealing with are exceedingly long in length. Since the thread length on A325 bolts is very short you should make sure they will be adequate for your application. ASTM suggests using A449 in lieu of A325 when a nonstandard thread length is needed. Here is an excerpt from the A325 specification:

This specification is applicable to heavy hex structural bolts only. For bolts of other configurations and thread lengths with similar mechanical properties, see Specification A 449.

For example, a 1” diameter A325 bolt that exists in the marketplace will have 1-3/4” of thread. There is a supplemental requirement in the A325 specification for fully threaded A325-T bolts that are 4 X diameter in length or shorter. There are often 1” diameter fully threaded A325’s that are readily available but they are no longer than 4” in length.

Portland Bolt’s position regarding ASTM specifications are that they are simply guidelines. They provide a buyer with a reasonable expectation as to the product they will receive if they order it to an ASTM specification. However, if the buyer and seller agree to change any portions of the specification, that is acceptable as long as the change is clear and agreed upon by both parties. Therefore, we frequently manufacture A325 bolts with longer thread lengths than “standard”. Since 1” diameter A325 bolts wouldn’t exist “on the shelf” with that nonstandard thread length anyhow (2-3/8”), it would make more sense to spec the bolt to A449 since it would be the proper spec to use and the bolts would need to be manufactured special regardless of which specification you choose.

Posted by Greg Lindsay

Phone: (800) 599-0565 Email: greg@portlandbolt.com
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The below content is submitted by readers and has not been researched or checked for accuracy. It is not endorsed in any way by Portland Bolt.

8 Responses to “Comparison of ASTM A325 and A449”

  1. Kumar Malde says:

    Your article about A325 and A449 grade bolts is very informative. I work in the wood connection trade and I wish you can include A307 as well in your comparison.

  2. Adam Oakley says:

    @Kumar Malde: ASTM A307 hex bolts are usually made using A36, a low carbon steel. This specification has a lower minimum tensile strength of 60 ksi and there are no yield requirements. There are 2 grades under A307, “A” covers headed hex bolts, threaded rods and bent bolts intended for general applications and “B” applies to heavy hex bolts and studs intended for flanged joints in piping systems with cast iron flanges. A307-A are wildly available in diameters up to 1-1/4” and are an industry standard for general construction applications. In comparison to the higher strength A449 or A325 these bolts will be less expensive due to the reduced material costs and fewer manufacturing processes. If you have further questions about these specifications for wood connection applications feel free to contact me. Thanks for commenting and your interest in Portland Bolt.

  3. Roger Plater says:

    Agreed this is very informative. I am working on a mid-80s oil installation. The drawings call up 42mm diameter ASTM A325 rod, 960mm long with 120mm threads at each end. It seems this diameter is no longer available in A325, but could these rods be obtained in A449? Many thanks.

  4. Tony B says:

    Great article, but it should be noted that using A449 bolts with diameters greater than 1.5″ have much lower tensile/yield strength. If you’re right at the edge of the limits of a 1.5″ A325 bolt & say you jump up to a 1.75″ A449 bolt, you go from an Fu of 105ksi to 90 ksi & an Fy of 81ksi to 58ksi. For combined shear & tension, this can have a big affect on your design. Plus the AISC Tension Stress Limit (Ft) formula is different for A449 bolts, than it is for A325′s.

  5. Adam says:

    It is important to note that ASTM A449 bolts are not permitted per AISC standards except for diameters over 1.5″ and in non-slip critical connections.

    • Dane McKinnon says:

      @Adam – yes you are correct when referring to structural steel connections where an A325 would normally be used. However AISC does permit A449 threaded rods and anchor rods in any diameter.

  6. Marlon Delos Reyes says:

    Design drawing calls for A325 M20x120 Full Threaded bolt. This is out of the box of ASTM Specification with regards to the threading requirements. Special fabrication is not practical since we are only requiring 24 pcs. for the project.

    Design team already confirmed that connection was designed as BEARING TYPE and that only SNUG-TIGHTENING is required upon installation. Can we replace it with A449? Eventhough it is clearly mentioned in ASTM A325 that A449 is the replacement material, are we not violating the provision in AISC-360M Section J3.1 with regards to the substitution of A325 with A449?

    • Dane McKinnon says:

      @Marlon,
      I am not intimately familiar with AISC-360, so I do not know how it is worded in regards to bolt substitution. You are correct that an M20 x 120 full threaded A325 is outside the allowable parameters of A325, so that puts you in a quandary. My opinion is that if your design team has given the OK to allow an A449 bolt in place of the A325, that should be sufficient. The engineer of record, if he/she is not on the design team, should also be consulted. ASTM and AISC are guidelines, there will always be circumstances that require adaptation.

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