you may be able to bore/ream them out but there will not be much material left (about .75mm) on the inner area which is 0.375" (about 9.5mm) if I remember correctly.
I drilled out the holes in the hubs to fit onto my drill motors which have a 9mm shaft. If you do this, I highly reccomend using a drill press with a vice to make sure your hole is straight.