Thanks for the information. Yes, the mounts are small flanges with 4
bolt holes. I will bevel the inside bore of my flanges, and build a
mount to keep the flanges from bending. Some 1/4" steel should work
pretty well. I'll probably step down the current one notch and take a
little more time in between each weld to minimize the heat.

Do you think that even if I sucesfully weld the flanges on the tube
without warpage (while mounted to some sort of support piece), that
when I remove the support piece from the flange, it will have some sort
of memory and warp anyway? It would probably be best to let the piece
completely cool down before I pull anything apart.

I could add some ribs to the flange, but I would have to start out with
a thicker piece and take off a lot of material. How tall and how many
ribs would you recommend for an 1/8" thick flange. It is about 4"
diameter with a 1 1/8 center bore.

I don't have the option to weld first and then machine. My mill does
not have the Z travel to accomodate my hub.

Before I begin machining a new hub I will try the old hammer and dial
indicator trick to see if I can true up my flanges. Maybe I'll get
lucky this time! Thanks.