3/8" A325 Bolt?? 5

[satchmo]

I have a drawing that calls for a 3/8" x 1-1/2" lg hex head bolt w/nut. The associated materials drawing states that "Structural field connections are to be 'Friction Type' and are to be made with high strength bolts (ASTM-A325). ASTM-A325 does not cover smaller than 1/2". Would A354 be an acceptable equivalent if I have spec a 3/8" bolt?

 

[hokie66]

In my opinion, a 3/8" bolt is not a "structural" bolt. Why not use the 1/2" bolt?

 

[MintJulep]

Why not ask the person that made the drawing rather than a group of anonymous strangers on the internet?

 

[metengr]

Maybe the person that specified what was required has passed away?

 

[MiketheEngineer]

Grade 5 or 8 would also serve the purpose - usually!!

 

[TVP]

Yes, ASTM A354 Grade BC are similar to the requirements for ASTM A325 for sizes < 1 inch in diameter.

 

[satchmo]

Thanks for the helpful replies. We wound up installing a 1/2" bolt. Maybe I should have given more detail in the question. This was a 1970's vintage dwg, and the actual bolt was missing from the structural member. It was inaccessible at the time so I couldn't get a measurement of the hole size. I was asking primarily to be prepared to have a 3/8" bolt as equivalent as possible to the A325 spec.

 

[port125]

That sounds like a typo. Should it be 3/4"dia.?

 

[Duwe6]

A325's are essentially equal to Grade 5's.

 

[stierman]

When inquiring into the interchangeability of SAE and ASTM bolts I have been told by two different Structural PE's on two separate occasions that the primary difference was in the materials.

Although SAE bolts and ASTM bolt have identical strength equivalents I have been told they have differing modes of failure due the differences in brittleness.

ASTM bolts are ductile compared to SAE equivalents and will yield more when over-stressed before reaching ultimate failure.

I’ve been taught that ideally in a structural connection such as a steel building the connecting members will fail before your bolts, i.e. bolts prying through a the plate in a shear tab.

The combination of the two lends to a more subtle mode of failure versus an explosive failure of a bolt reaching its ultimate strength.

 

[Guest102023]

Why can't 3/8" be a structural bolt? It all depends on the scale.
In the Meccano universe, No. 10 is a structural bolt ...

 

[Screwman1]

The OPs drawing calls for an A325 bolt and that standard does not go that small; so he can't meet the print requirements. You can't have a 3/8" A325 because it isn't in the standard.

 

[moltenmetal]

stierman: you forced me to look this stuff up!

We agree that the tensile and yield minimums are the same betwee A325 and SAE gr 5 bolts.

ASTM A325 type 1 bolts are medium carbon, carbon/boron or low carbon steel, quenched and tempered. Elongation in 4D is 14% min and reduction in area is 35% min.

SAE J429 grade 5 is typically paired with ASTM A449. These bolts are also medium carbon steel, quenched and tempered, with 14% min RA and 35% elongation.

The bolts would appear therefore to be identical except for dimensions, the A325 bolt having a shorter threaded length (i.e. better suited to use in shear connections) and a larger head (i.e. a "heavy hex" head).

Is there really a difference in the ductility of these fasteners?

 

[moltenmetal]

Sorry, where I said "low carbon" I meant "low alloy".

Note that what we're talking about is not substituting SAE gr 5 for A325 construction bolts at sizes 1/2" and larger. We're discussing whether it's necessary or even a good idea for people to substitute 1/2" bolts for 3/8" bolts in a design purely out of a concern over the properties of the bolt material between the two grades. I know the AISC manual doesn't deal with fasteners smaller than 1/2" and that the A325 spec also starts at 1/2", but that shouldn't stop people from using 3/8" bolts in structural applications where they're appropriate.