Breadboard vs Steel to prevent table warping
I am building a solid wood plank dining table for my daughter. She wants the top 60″ x 36″. I am making it from 6/4 Red Oak.
What are the advantages of different anti-warping methods?
I have considered breadboards on the ends, and steel on routed cross grooves on the bottom with slotted punchouts to allow moisture expansion.
I have seen how to make a breadboard with a full length mortise pegged to the planks, glued only in the middle, with slots in the tenon to allow expansion across the width of the planks with moisture changes. However, I see many solid wood plank table tops in restaurants that do not seem to have the end breadboard attached with expansion in mind. When I look at the finish, there seems to be no movement in the joint between the breadboard and the planks. No obvious pins to hold the breadboard to the planks. Are these tables relying on moisture blocking finishes, near constant humidity in the environment to reduce expansion, or are they going to have a problem in the future? Or am I just inexperienced in looking at how the breadboard is attached?
I have seen metal cross braces with slotted screw punch-outs, that will allow the lateral expansion of the planks while the screw slides in the slot, but holds the planks down to prevent warping. I imagine that two screws per plank would be good to hold it down, with 3 lateral steel cross braces in the 60″ table.
Another method would be to use wood cross braces, screwed to the planks, with the backside of the hole in the cross brace enlarged to allow the screw to flex while the planks expand.
I also believe the bottom of the table top should be sealed in the same way as the top surface to provide as even as possible moisture absorption blocking through both top and bottom surfaces of the planks.
What methods are time tested and reliable, and what are the advantages you find in terms of construction difficulty and appearance that are recommended for this?