It is common for ASTM A325 to be specified by engineers based on the strength requirement of the grade, but often times the size availability and allowed configuration is not considered. For example, an engineer may specify an A325 in longer lengths than what is readily available or incorrectly as an anchor bolt due to the minimum yield and tensile requirements. A325 bolts are also often incorrectly specified as threaded rods or specified in diameters larger than 1-1/2″. Custom sized A325s can be be manufactured, but this raises the question, is there a fastener grade that has similar mechanical properties, but is available in larger sizes or can be used in applications other than steel to steel connections?
Similar Grades
A325 Mechanical Properties
| Size | Tensile, ksi | Yield, ksi | Elong. %, min | RA %, min |
|---|---|---|---|---|
| 1⁄2 - 1 | 120 min | 92 min | 14 | 35 |
| 11⁄8 - 11⁄2 | 105 min | 81 min | 14 | 35 |
ASTM A449
Mechanically and chemically, A449 is virtually identical to A325
| Size | Tensile, ksi | Yield, ksi | Elong. %, min | RA %, min |
|---|---|---|---|---|
| 1⁄4 - 1 | 120 min | 92 min | 14 | 35 |
| 11⁄8 - 11⁄2 | 105 min | 81 min | 14 | 35 |
| 15⁄8 - 3 | 90 min | 58 min | 14 | 35 |
SAE J429 Grade 5
SAE J429 Grade 5 fasteners are typically used in the automotive industry or OEM type applications, but much like ASTM A449, are very similar mechanically and chemically to ASTM A325.
| Size | Tensile, ksi | Yield, ksi | Elong %, min | RA %, min |
|---|---|---|---|---|
| 1⁄4 thru 1 | 120 min | 92 min | 14 | 35 |
| Over 1 thru 11⁄2 | 105 min | 81 min | 14 | 35 |
Other Configurations
ASTM A449
Where ASTM A449 becomes a potential alternative for A325 is when the strength of an A325 is desired, but the actual part is an anchor bolt or a configuration other than a heavy hex bolt for steel to steel connections. ASTM A449 covers headed bolts as well as bent bolts, and threaded rods. Another thing to note is that A449 covers diameters ¼” thru 3” whereas A325 is restricted to ½” thru 1-1/2” diameter. This will likely not solve the issue of availability however since A449 fasteners often times are not readily available off shelf and would need to be manufactured on a per order basis.
SAE J429 Grade 5
The main difference that you will find with Grade 5 bolts is that they have a standard hex head as opposed to a heavy hex head and a longer thread length since they are not specific to steel to steel connection applications. Although it is recommended that a user confirms the standard hex is acceptable before substituting for an A325, they may be a viable option since they are readily available in longer lengths than a standard size A325s.
ASTM F3125 Grade A325
In the past ASTM A325 was specific to heavy hex head bolts with shorter than standard thread lengths only. However, with the implementation of ASTM F3125, this is no longer the case. Although the specification still requires the bolt to be used in a steel to steel connection application, it allows for the head to be something other than a heavy hex pattern, such as square head, carriage bolt, standard hex, etc. It also allows for the threads to be longer than standard if needed. One thing to note is that if the head configuration is different than a heavy hex or if the thread length is longer than standard, the head of the bolt must be stamped “A325S”.