Changed my plugs this week, three broke and two left the porcelain in the head. To get them out I used a method that I haven't seen described anywhere that worked really well.
I used a #2-56 screw glued into a 2" #4-40 standoff as the "pin" to glue into the porcelain. For the "extractor," I drilled and tapped a #4-40 hole in the end of a 3/8" threaded rod and put a #4-40 screw in it. Essentially it was a threaded rod with a smaller threaded rod sticking out of one end. The extractor then screws into the end of the standoff part of the "pin." You use the same method to extract the porcelain as you would the ground shield with a threaded rod (described in this thread
). The pins are sacrificial, but the extractor can be used over and over. It worked like a champ. Also, you can use the other end of the rod to extract the ground shield.
And if there's any interest, I could build more and sell them for a small fee.
Here are two of the "pins." The top one has porcelain attached. The bottom is unused.
Here is the "extractor." The right side is the tip, with #4-40 screw.
Here's an up close picture of the extractor tip.
Finally, here's an unused pin threaded to the extractor.