A325 Bolts 2

[Cranehook]

Anyone know a substitute spec for A325 bolts? Have existing 1 3/4 dia bolts in a slip critical connection that need replacing. Dwg specifies A325 but max bolt dia in spec is 1 1/2". Vendor wants to sell me SAE J429.

 

[btrueblood]

A325 Type 1 calls for medium carbon, Q&T steel, type 2 low carbon martensitic Q&T steel. For both, min yield 81 ksi, min. ultimate 105 ksi.

Because the spec. is limited to 1.5" max. diameter, there is some question about what strength the application really requires - i.e. in ASTM A449, which is also a medium carbon Q&T bolt, diameters from over 1.5" to 3" have a min. yield of 58 ksi, and a min. ultimate of 90 ksi. That's a big jump in yield strength...

SAE J429 is not going to get you there either - that spec. only covers up to 1.5" diameter also. Furthermore, your vendor should have added "Grade 5" to his recommendation, because without that, you could have gotten plain carbon steel bolts ("Grade 1") with 33 ksi yield strength. Also, SAE specs may or may not "meet code" for your application.

Two recommendations for you: come back with what tensile/yield strength your fastener needs, and what the governing standards (if any) for your application are, and people here can help you figure out a spec. to purchase to.
Second recommendation -- if you need to purchase bolts to specific standards, find a different vendor, because the one you quoted doesn't sound like much of an expert!

Sorry I can't help you out more than that

 

[Ron]

Consider using ASTM A490 bolts.

 

[btrueblood]

Um, A490 only covers up to 1.5" diameter bolts also.

 

[UcfSE]

btrueblood, A490 bolts are stronger than A325 so the 1.5" A490 might work where a 1.75" A325 does not. He'll have to check the loads to know.

 

[Cranehook]

Situation: Existing 1 3/4" A325 Ty 1 bolts for a 100T Halter Marine floating crane require rpl due to corrosion. Mystery is where did they come from since max dia A325 is 1.5". A325 is specified on dwg and bolts have A325 markings.

Don't have orig calcs so actual loads are unknown and diffucult to calc. Changing size of bolts is not an option.

J429 GR 5 and A449 have same mech props as A325 Ty 1. Problem w/A449 is AISC forbids use in slip crit joints.

A354 is another option; spec states Gr BD can sub for A490 w/caveats, but is silent as to A325. Looks like Gr BC is similar w/Fy=109k & Fu=125k.

It's just odd to me that A325 spec gives little guidance for larger than 1.5" bolts.

Bottom line is I need to find equal or better bolts that can be installed as a stuctural slip crit fastener.

 

[Cranehook]

Forgot to thank those that responded. Thanks much!

 

[btrueblood]

Cranehook,

Well, let me preface by saying I don't know much about AISC and what it says about slip critical joints. But here is a list of spec's. for bolts with equal or higher tensiles relative to A325 at 1.5", but in sizes thru 1.75" or higher:

ASTM A320 (yld 105 ksi, ult 125 ksi, 1/4 - 2.5")
A354 Gr BC (yld 105, ult 125, .25 - 2.5")
A453 Gr 660 or 662 Class A (yld 85, ult 130, .25" and larger)
A687 (yld 105, ult 150, .625" - 3")

It doesn't sound like it, but if you could use a metric bolt, there are some ISO standards that you could probably use, and we've found there is a higher likelihood of finding available supplies for ISO fasteners made "to spec".

Good luck.