A handy set of tools

[coolmercury]

In years gone by when you screwed up a head by stripping out a spark plug hole you needed this kit.  The top item is the reamer with four sizes----you used the next size up from the stripped size and then used the proper tap to cut new threads.  Then you used a new spark plug to match the new size. 

[bonneyman]

Ouch, sounds risky! How do you ensure you get all the metal chips out of the bore before starting the engine?   
If the chips were steel then a magnet would work. But heads have been aluminum for quite some time - wouldn't work on those.

Cool tool though! Looks like the forerunner to Helicoils.

[john k]

what I have seen guys do is hold a vacuum cleaner hose over the spark plug hole while the engine is cranked.  With aluminum shavings,  most should pass through the exhaust valve.

[fatfillup]

I had one of those kits, I think it sold