[blykins]

Steve, my setup is like Syd's...the only thing that is missing is the lower shaft in his picture. As you can imagine, that upper shaft will just slide down inside of it, and the roll pins secure it.

The flanges were cut on a lathe.

I will bolt them together....then slide it on both shafts at the same time and then weld.

I would think (and hope) that it will be square that way. If the bolts are already in the flanges and they're clamped together, they should already be "preloaded" in the correct position. The only other thing I can do is use a square when putting them on....tack it on....then move to the next 90 deg....square...then tack...etc.

The flanges are 1/4" thick...it should have enough meat to square itself up as it's being slid on the shaft.