Choosing the bolts that are right for your job

I am often asked about bolts and bolt maintenance on billboard structures. The first thing I always say is to defer to your engineer.  But there are some basic things to consider after your engineer gives you the size and strength requirements for the specific connection he is evaluating. The connection that most often comes in question is the “head” connection. That is where the torsion tube is connected to the column. Depending on the bolt and type of connection your engineer has specified your suppler will have some additional choices to make. These choices will make a difference in the quality and the cost of your job. 

First a discussion about bolt grades. Over the years I have seen four grades show up on structures. 
Grade 5
Grade 8
A325
A490 

At All Steel Structures we do not use Grade 5 or Grade 8 bolts in your structural connections.  Although when you look at the strength charts these bolts are similar to A325 & A490 respectively they are not interchangeable and therefore we believe they have no place on your signs. 


Next when purchasing bolts we have a choice between types and coatings. Types refer to either Type 1 which is most common and is made from Medium carbon, carbon boron, or medium carbon alloy steel. The other is Type 3 which is made from weathering steel.


Coatings options are:


For A325 bolts:
Plain
Zinc
Cadmium
Galvanized

For A490 bolts:
Plain
Dacromet

Both A325 and A490 bolts can be painted after installation.

Give us a call to talk in more detail about what is the best fit for your project.