https://www.mccoys.com/shop/p/6127534-052303-28/waddell-2752-top-plate-steel-zinc
Has a #18 thread size with 5/16 in Dia.
Type
Angled
Thread Size
5/16-18
Mounting Type
Screw
Dimensions
2-7/16 in L x 2-7/16 in W
Material
Steel
Finish
Zinc
Suitable for
Table Legs
Includes
5/8 in Mounting Screw