I used to have a bunch of British cars -- TR's mostly.

They were easy to work on -- cheap and fun - by the time we got them in the late 70's they were tired -- cross threading was a common problem (does any one remember how often one had to pull plugs in cars from the early 60's)

Most of them would have the first few threads crossed or sometime it would just be a check in the first thread -- A tap would straighted it all out and clean it all up. Not much shavings involved you are not cutting -- just pushing the thread bact in its proper place

It is not normally needed to hell coil - even in Al you really need to put the plug in wrong and then be foolish enough to believe that it requires that much force to put it in - of