Do you use anti-seize compound?

[ACE]

This stuff rates with duck tape. Never be without it!
ACE

[xs11jack]

Anit-seize compound

I use the silver, sparingly on plugs and on disimmular metals. I bought an 85 H---- I just can't say it, a few years ago, and I can sympathize with Dragon Rider, although I found a solution, which is take the head off, no getting around that, and take a 32 TPI hacksaw blade and grind the back down, (cool it often to save the temper) to about 3/16th of an inch and put it in one of those cheap plastic handle that slip on the blade. Next, with the head on the bench with the combustion chamber facing you, VERY carefully saw a slot in the broken plug. Stop frequently to observe the depth of the cut, stopping when you see a hint of the aluminium threads!! then make a second cut about 120 degrees from the first cut and a third 120 degrees from the second cut. When finished cutting take a small screwdriver and gently tap the segments inward, that is toward the center of the plug hole. the tapping will break the uncut metal and the broken pieces will come out without any real damage to the thread in the head. Just as a precaution I took the head to a friend that had a thread chaser of that size and had him clean it up. He told me there wasn't really anything that the chaser cleaned out. It doesn't take a lot of skill, I don't have much, just patience. It took me about two hours to get the fragments out.