Beware the spiral EZouts. They usually wedge in and tighten the broken bolt even worse thsn it is. See if you can find a square EZout. They work 1000 times better.

Another thing worth having in any shop is a set of left hand drills. You can often get the broken bolt out just with the left hand drill, before even resorting to the EZouts. Trick is to step drill, starting with a very small one. If that one doesn't back it out when it breaks through the bottom, go up one size and try again. Spray some WD-40, Kroil, or other penetrating oil in the hole now, too. If that one doesn't grab and back it out, then repeat until you are about 60% or so the diameter of the bolt and then use the EZout.

BTW, I am a machinist at a pump shop and remove broken bolts almost daily from cast iron, stainless. bronze and aluminum parts.