Cleanout pipe threads destroyed

[Pman6]

I have a home built in 1966 with metal drain pipes.

Cleanout plug was removed in the distant past to service the pipes.
Plug is missing. So the cleanout leaks a little water to the outside when the kitchen sink is heavily used.

2.5" brass plug seems to be the right size, but the female pipe thread is gunked up nasty with some hard caked on crap, and actually looks out of round.

I think anyone would conclude it would be impossible to screw a new plug on there.

How do you clean up the gunked up threads? I tried some paint and epoxy remover chemicals, but that didn't work.

If you couldn't get a plug into the threads, how would you solve this problem?
Is there such a thing as an adapter you can weld on with fresh threads to fit another plug?

 

[Reach4]

Try a wire brush.

You might be able to use a "test plug".

I have not tried this: http://www.ipscorp.com/plumbing/testtite/mechanicalplugs/tconecleanout

 

[Sponsor]

 

[Craigpump]

Rent a pipe tap of the right size

 

[Pman6]

I used a wire brush by hand already.
Maybe I'll try a drill attachment.

The test plug and pipe tap sound like good ideas, but 2.5" ones are hard to find.

why did they have to seal the clean out plugs so tight.... I see other people have the same problem with corroded threads or caps that need superman strength to remove.