Best thread repair for spark plug port

I'm sure that I read somewhere in the heavy maintenance manual that the spark plug threads cannot be repaired with a helicoil but I cannot find it in the latest version. I've certainly used helicoils to repair plug threads in automotive engines.

If you have minor thread damage then you can use a reverse action thread cleaning tool like the one shown here: https://www.youtube.com/watch?v=K1BhfhsinJs

I've had success using these in the past, just make sure that you have the correct thread size and pitch.

Either one of these will work for most jobs. 
Plugs should always be screwed in by hand and they should thread all the way down easily.
I never use a wrench on a plug until it bottoms out before it gets tightened.
I use the smaller black 12mm chaser (2nd one posted) most of the time and have never had an issue.
Always lube the thread chaser threads before use.

Thread chasers usually just re-shape the threads and don't have real sharp cutting edges like a thread tap
because your just re-shaping the threads and aren't cutting new threads into something for the first time.

https://www.amazon.com/Powerbuilt-641148-12mm-Thread-Repair/dp/B001SOHXLQ/ref=sr_1_1_sspa?adgrpid=1337006709580694&hvadid=83563084983477&hvbmt=be&hvdev=c&hvlocphy=45203&hvnetw=o&hvqmt=e&hvtargid=kwd-83563276507906%3Aloc-190&hydadcr=24625_10488455&keywords=12mm%2Bspark%2Bplug%2Bthread%2Bchaser&qid=1684762515&sr=8-1-spons&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFLVEg5VTg0SkM1UkMmZW5jcnlwdGVkSWQ9QTAwNzEzNTgyVzdSVVdIMDVQRlNJJmVuY3J5cHRlZEFkSWQ9QTAzODI4OTYyUDRONlpEOEtQTEFQJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1

https://www.amazon.com/Lang-Spark-Thread-Restorer-LNG-1013A/dp/B007TX0966/ref=sr_1_5?adgrpid=1337006709580694&hvadid=83563084983477&hvbmt=be&hvdev=c&hvlocphy=45203&hvnetw=o&hvqmt=e&hvtargid=kwd-83563276507906%3Aloc-190&hydadcr=24625_10488455&keywords=12mm+spark+plug+thread+chaser&qid=1684762713&sr=8-5

Thank you for the tip.  Hopefully, the threads can be realigned without too much loss of material.  Torquing the plug to specification will be the stress test!

RW

Thanks again Roger.

Rickey Wiseman