Tapping a 7/16" X 20 TPI thread into 1/2" mild steel

I've used this method a lot. It work great, especially with soft metals like aluminum, copper, brass and plastics where its easy to to start crooked and strip.

Why 7/16 fine? It isn't overly common unless you have a really good hardware store or order the bolts and stuff you need.

Big enough to be strong, but not so big that it gets in the way, and lots of thread area for its size.