re: Repairing cast iron drill

Perhaps leave the stub and drill a smaller hole that you can epoxy an aluminum or brass rod into.  Then put some JB Weld  putty around the dowel and while it is still pliable, press it and thread it into the handle so what putty takes the shape of the inside threads.  After the putty sets, use the hole in the handle to drill the hole for the roll pin or whatever you use to prevent it from spinning.  It looks a little small but if there is enough meat after drilling the hole, perhaps you could cut some threads on the inside of the hole it and on the rod to give the epoxy something to grab on to.  

You could just use threaded rod instead of brass or aluminum but I figure the softer metal would be easier for drilling the cross pin hole.