I was looking at clamping down a 4x4.75 inch plate to my H7527 rotary table, and decided to get some different hold downs. I had used the wimpy 8mm bolts, and just fer snorts n giggles, I measured the slot width. 0.422... Looked at my chart... 3/8ths...
For those using this table, the 3/8 x 16 stuff you have works.