We run into this quite often. The tool from Technic Tools takes to long. We purchased a 1" hollow mill (1/2 HSS - dolfa 5-540-060) from Nate's Industrial Tools, Inc. in Torrance, CA (310) 325-6262. This fits over the broken bolt and just cuts the outside. Snap-On supplied us with a tool to hold the mill from the inside that allows us to connect the mill onto the drill. The new Snap-on rep. cannot find the part/part no. for this tool again. The mill takes off some of the metal from the rim away. We put a modified washer with the new lug bolt. This gets pressed in and stays there forever. This job you can do in 10 minutes.
Good luck;
Jean