Hanging signs (and most other signs too) need some structure inside to make sure they stay where we put them. Over the years they will be subjected to winds and gravity. Plus there is always the macho dude who sees something like a hanging sign and suddenly he has to prove how tough he is by jumping up and doing a few chin-ups for good measure. I want to be sure that no matter what the signs we build will withstand whatever might happen. A welded steel internal frame is the best bet that will be so.
In this case the frame is made from 5/8" solid steel bar. It[s probably overkill but I know I will sleep soundly knowing the sign won't break apart with this inside. The cast steel eye bolts are rated for 5000 pounds each - more than enough! Once the frame was welded I laid it on the back of one of the sides of the sign and marked it out. Then using the die grinder I cut in a 1/2" deep slot. I repeated this step on the second side as well, test fitting dry to make sure everything lined up tight.
Then I spread on the Coastal Enterprises PB Bond-240 glue which is formulated for Precision Board according to the directions. I misted the Precision Board with water to activate the glue and clamped it up tight. Tomorrow, once the glue has cured I will hang the sign and glue on the other four pieces. Then it is time for a little finishing and paint once more.
The end result is a sign with hangers that is plenty strong!