"The real facts" are that you earlier posted that it would be fine to do "quite a bit" of filing with a bastard file on a new iron plated tip. Now you've changed your tune to using only very fine abrasives.
I didn't change my tune. You never had any reading comprehension.
If the file were all you had, and your iron didn't work, you could clean a Hakko* tip many times with that bastard file before you ruined the tip. In fact, it could potentially live a full life and die of other causes... the chrome flaking off or wearing through. Or the insert in the back falling out. I continue to stand by this point. What I actually said was:
The iron layer on some irons is very thick and a new one could be filed quite a bit with a bastard file before you erode all the way through. The extra thickness is there so they last longer. Of course, you would want to remove as little good iron as possible. Sanding with fine grit paper might be perfectly fine.
You say:
A file will remove more than .012" in one swipe.
Sure, if you want to kill the tip, you could file it like that with a nice sharp file. You could put the tip in a vice, put all your weight into it, and even dig in the corner of the file for good measure. With a good enough technique you could cut the tip right in half with one good stroke!!! If that's what you think the OP would do to clean microscopic surface rust after reading the comment, above, then I thank you for pointing out my mistake of assuming at least few IQ points of the OP. If you can't do sub 1 mil work with a file, I just don't know... Heck, if I had a file that automatically took 12 mil on every stroke, I might not need an angle grinder. But I sure as hell would need a finer file.
I'm guessing you're a young kid who just doesn't know what he doesn't know yet. You'll learn.
We all don't know what we don't know.
But you're the guy that is refuting my statements based on marketing literature... of which you don't even have a grasp of the numbers you are arguing about. The fact you think it contradicts anything I said shows me what you don't know.
That is your great contribution to the thread, and for that we all owe you a big thanks!
By all means continue to twist my words. The posts are there if anyone cares to read them in context. Go 'head and cherry pick. String 'em up however you like. What I shared here, I know because I have BTDT, and I stand by everything I posted, here.
*Ersa users, this has nothing to do with your iron of choice. I'm sure Ersa tips are exceptionally well made, and I bet they taste great, too. I hear they last ten years with heavy use.
I find it very hard to believe that there would be any machining done on a soldering iron tip. There isn't room in the price. I would also find it very hard to believe that the iron layer on any tip is more than a very thin layer. Certainly not thick enough to be machined or even filed on without removing it.
If it would satisfy your curiosity, I could show you this is the case. Pics through a USB microscope of a new clone T12 tip showing the obvious and huge machine marks under the chrome and on the wettable area of the tip. Then another pic after filing the tip and through the chrome until the areas are covered in new files marks in a different direction. And a third pic after finish sanding totally smooth. And there will be no copper pinholes. Even you state the layer (on an Ersa tip) is 4-12 mils thick, and you, a professional machinist, find it hard to believe this could have been machined? First off, that would be what's left AFTER the machining. Second, to hell with the bastard file. I reckon I could resurface a 4 mil layer of iron with a die grinder and a carbide burr, completely freehand. Maybe more than once. This is why I call it the iron layer. Because 4-12 mils is really, really thick for something called a plating. Think about it. You read "plating" and make assumptions about what you can or can't do to it. You read 4-12 mil, and you have no grasp of that as a machinist? If anyone should want to backtrack, it is you, my friend. Just say the word, and I'll make you eat yours.