The drill jig I made up was designed so that when you slide the finished hub onto the axle shaft ... line up the drilled holes ... the shaft end is flush with the end of the hub.
Here's a quick shot of the MIG welder that I am using. I have a large roll of flux-core wire inside ... that feeds out when I squeeze the trigger. I am not using an inert gas (like CO2 or Argon) ... just the flux-core wire. It does splatter a bit (little beads of excess wire) that usually wire-brush off ... or can be knocked off with a file. And they leave little brown burned speckles all over my wooden workbench top. Which is why welders usually top their workbench with 1/2" plate steel ... to which you can "tack" parts to keep alignment before welding them up together. To get your finished piece off the table ... just grind off the "tacks." And use the portable hand-grinder to smooth the workbench top.