How many times my plumbing days have been salvaged chiseling seized bolts out. Learned from my early days with no torque wrench on my dirt bike. There is a bit of skill involved, and a good sharp Klein screwdriver? No, kidding about the screwdriver, the handle will/could shatter. My favorite is a through handle wood chisel, the steel shank goes all the way through. Orange steel chisels are a joke. They have to be made soft for safety? The older dark chisels rule! And do shatter once in a while. Drive a notch towards the outside as far as you can, straight down, then use the notch at an angle to drive it out counter clock-wise. I would use a chisel about 1/4" wide on that one. The left handed drill bit takes some thinking to grind! And run the drill back wards, its way cool when it works. It already has a hole in it, but the proper size easy out is important, and I am not a big fan, especially when they break. They are made of the good steel though, and will shatter for removal. I would probably try to warm the surrounding case some also. It should come right out, unless the threads are crossed. Just a matter of getting some torque on it, in the proper direction! Vintage Bob