then carefully drill the bolt out, it will take forever so take your time, I have set up drills with blocks and bungee cords so it will drill itself without you being in atendance, but the drill has to be positioned precisely as to not damage the inside diameter of the threads for when you install the new bolt. If you have the head of the bolt and any threads showing you will have to fid a HSS Drill bit a little smaller than the outer diameter of the threads. If it broke off you may not be able to get it out with an extractor set but use the biggest extractor that will fit.
You could first try an extractor set, it will have to be drilled to the size on the extractor set, use a product called PB Blaster and let it soak for a few days reapplying every 12 hours or so. You will have to drill the bolt out completely.
