This subject came up on a Facebook group I belong to and when I posted the so called Clean out screw actually wasn't, that it was left over from the manufacture process and should be left alone I got well roasted.
In 30+ years of shooting have never had to remove that screw for any reason on any of my percussion guns.
If it was posted on Facebook then it MUST BE TRUE!!
They have 'Fact Chechers' ya know.
'Cross thread's and 'Stripped threads' come from those who don't know how to the screw and/or do know use the correct tool and size for the job.
I remove ALL my nipples and touch hole liners when cleaning and have not yet to cross thread, strip, nor damage a one.
Can they be 'damaged/weakened' by removing them, cleaning both male and female threads and the lubing them and tightening them back?
YES; if you:
1) Don't clean all the crud from all the threads before replacing.
2) You over tighten them upon replacing.
3) You don't properly align the threads BEFORE screwing it down.
If you have one 'worn' to the point that it is able to 'Blow Out' and you did not notice how ill fit it was; I would suggest letting some else do it for you or leave them alone until the rot out.
HOW TO SCREW A SCREW:
1) Using Fingers, NOT a power tool or magnetic driver, you align the threads by Gently turning Backwards (generally counterclockwise) until you FEEL the slight 'drop' - that is the beginning of the two threads Mating ritual.
2) GENTLY reverse turn and it should begin to seat and the screw, nipple, liner should begin to drive into the female threads.
3) IF both sides are properly cleaned, undamaged, and the male properly lubricated then it should twist and slide right down.
*often recommended if not a 'torqued' or permanent mount: reverse once more a few turns to further disperse the lubricant to the female threads.
4) Once the male reaches bottom, or as far as fingers will go then, using a Properly fitted tool and Gently tighten it fully, but Not Torqued unless noted in manual.
IF at any point you feel ANY kind of resistance; Pull the screw, liner, nipple back out and find out was it WRONG!
Ignoring and continuing Will Result in a Stripped or Cross Treaded or at the least Undue Wear on the threads.
There: there is your Mechanic Porn for the day.
Follow use proper caution and protection and you won't ruin those threads and some day have a Blow Out.