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bolt specification question

State WI
Description Text

WisDOT is putting together a detail for double faced thrie beam based on SGM09.  The SGM 09 detail uses FBX16a bolts to connect the modified steel block to the steel post.  The guidance in the standardized guide for barrier hardware indicates that FBX16A bolts require the use of   ANSI B18.2.1 and ANSI B1.1 for Class 2A tolerances.

Why is ANSI specification being used instead of ASTMs?

I was also trying to dig up guidance on the nuts and washers for this bolt as well and have not had much luck.  Do you have this information or could direct me to the correct sources

I know that contractors and construction staff are use to looking for ASTMs or AASHTO’s specifications and I’m trying head off phone calls ( e.g. is this the correct stuff, why did you use this verses this, why did you use an outdated materials specification….).




Other Keywords Thrie beam double faced
Date September 10, 2013


The bolt spec you are looking at in SGM09 is referenced in metric because at the time of the hardware guide publication, there was a push to switch to metric units. 

For FBX16a, the hardware guide requires ASTM F568M Class 4.6 bolts for galvanized hardware. ASTM F568M is an ASTM International standard for metric bolts, screws and studs. Class 4.6 refers to the grade. ASTM F568 defines materials used for manufacturing a broad category of fasteners with a wide variety of materials strengths. All metric fasteners are made using materials that are specified in ASTM F568.

The Class 4.6 specification is essentially the same grade as the ASTM A307 spec. It does not require heavy hex bolt and nut configuration, but I can see no problem with using heavy hex or structural bolt sizing. ASTM A307 can be obtained in heavy hex or standard configurations. A307A is standard bolts and A307 B is heavy hex.

Nuts for ASTM A307 are A563A Heavy Hex or A563A Hex and washers are F844.

Date September 11, 2013

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