How do you take the center hub cap off?

1/4 inch bolt has a 7/16 head ( not that its a big deal ).
Seems like 100 years ago now when I had loose rattling centers on AMC Gremlin X wheels. The threads were shot. I thought I would be smart to retap every hole to 5/16 and put a new bolt in every hole. Guess what ? The 5/16 standard bolt head is 1/2 hex and too thick to let the wheel mount properly also. I had to countersink evey hole in all 4 wheels and use flat head machine screws, flat head screw driver and all.
Fun fun