Hi,buck

For what your doing, there really is little reason to get fancy,or spend cash on a new boring bar.

The pic’s are just something off the'net, but do show the idea.

Just grab a piece of mild steel bar stock from your scrap bin, turn one end so it will have a little clearance in the bore of your hub,and long enough to reach well past the end of the hub. Making it rather large in dia. will keep the bar nice and stiff.

Next, drill a ¼” through hole in the side of this bar, 90 degree’s to the bar center line in your drill press for the cutter bit. Maybe start about ¾ “or so,from the end of the bar.The round tool bit hole will be fine for this little job cutting aluminum.

Now drill and tap for a bolt in the end of the bar to hold the bit,maybe ¼-20 or so, this will square up the bit in the round hole as it is tightened.

If room is a problem,just scale down the boring bar.

Turn/grind, whatever works,the opposite end of the bar to fit in your tool post.
Grind your clearance rakes on a short tool 1/4" square bit, and have at it.

Practice on a piece of scrap stock with the hub bore size drilled in it first.

Once again,no reason to get all fancy,with broaches for keyways unless your doing a pile of them.
Good Luck.