Mike

I learned a trick many years ago with stubborn snapped bolts or studs that "easy outs" wont budge.

Drill the broken piece out it's full length (i.e. right through) and then increase your drill diameter until almost to the thread. This will usually be on one side as it's impossible to drill the hole perfectly central. Then get a new fine (I think about 32 or 36 teeth per inch??) hacksaw blade and grind the end thats away from you when cutting down for about 1 1/2 inches so it's thin enough to go in your hole. Holding the blade in your hand or a vise grip you can then cut down into the thread on the thinnest side until the blade has exited the edge of the bolt. Depending on how much of the bolt remains you will need to do it again at about 180 degrees so you have 2 separate pieces you can disentangle from the threads and prize out. (I have had to do 3 cuts occasionally)
Your threads will have 2 grooves cut in them but it makes no difference once a new bolt is put in. If necessary clean out the thread with a tap. I was shown this by a tractor mechanic who removed a big 1/2" snapped exhaust manifold stud from a John Deere tractor head and a new stud was installed and torqued up no problem afterwards. I've had occasion to use this method several times in the 30 years since.

Justin