[spiff]

Before you chase the thread from the outside in, there's a product that a friend used that actually cleans the thread from the inside out. From what he described, it's a collapsable tap that you insert into the bottom of the spark plug hole, then expand the tap to mate up with the good threads at the bottom. With grease previously added, you unscrew this to clean the threads out and the chips get pulled out instead of pushed in. I'll try and find the name of the product. He said he found it on the web. Specifically made for stripped sparkplug threads. Cost was about $60. Saved him a whole lot of hassle that you describe.....