I am looking to build my own "wrought iron" fence. I have a welder
friend that will help me assemble.

The design I was thinking was a basic flat top rail with square holes
so that the pickets come through the top rail 4 inches.

The pickets would be 5/8 inch squares and the top rail should be 1/2"
thick. So I need to be able to make a 5/8" x 5/8" square hole in 1/2
in inch steel.

What is the best way to do that, considering I need to make about 100
holes in 25 feet of steel.

I was going to hire the fence building work out but I am getting prices
in the $75 a linar foot range for this fence and figure I could it for
a lot cheaper.