Dont let expansion and contraction stop you from putting a wood top on your new steel base. These brackets will allow the wood top to move freely as it likes to move with temperature changes. Just make sure you weld it on your base with the slot facing perpendicular with the wood grain.
LivingOG Bracket's - Wood to Steel application
Material - Carbon Steel
2.5 inches long X 1.5 inches wide.
9/32 inch wide slot X 1.5 inches long.
1/8 inch thick .
.01 lbs. each