aim cylinder shaft: thread size?

I was able to salvage my lower can bracket. Got the shaft removed with the good ol breaker bar on a pipe wrench.

Now my last problem is rust on the bracket. There's rust blocking the hole. So I need to "tap it". lol

So does anyone know for sure the thread size on an aim 3" cylinder shaft? Would it be metric or standard? and what size? fine thread?

Thanks for any help. As soon as I "tap it" lol, I'll be back on the road.