the bolt that broke.... the head broke off it?
and the other end, it threads into something? In other words it doesn't have a nut?
If it doesn't have a nut, but the other end of the bolt is exposed and accessible from the other side of the hole its in, locate the center of the bolt, center punh it and drill it out, threads and all with a drill bit the same size or alightly small than the diameter of the bolt. Then when you get the bolt out install a heili-coil to restore the threads. When you drill the bolt out start with a small pilot drill about 1/8 or a little larger and work up in size gradually. Run the drill slow because the bolt is hard and be sure to use plenty of oil/coolant. I like to use WD40.
