Let me qualify the title: you cannot tune metal unresponsive yoyos by re-orienting the halves relative to one-another*. *unless they use Side Effects
The theory I’ve always operated under is that the whole teflon tape technique allows you to shift how the halves are oriented with one another. I’ve even passed this misinformation along to other people. But it doesn’t. It’s so obvious now when I’m thinking about it, but it wasn’t intuitive so I never clued in.
For the uninitated, the theory presented is that you put teflon tape around half of an axle and put’er in (I usually screwed the bare side all the way into a half, and then screwed the whole thing together which would cause the teflon tape to engage). If your yoyo has vibe, you unscrew. The taped side should “stay put” when you do this. Then using a hex key, you turn the screw a small amount and reassemble the halves, which should now be reoriented relative to one another by that small amount.
But that’s not what happens. The math doesn’t work that way. The threads are a constant and the bearing width is a constant. If you turn the screw 1/4 of a turn, when you put the other half back on, it is also getting threaded by that exact same 1/4 of a turn difference! Your halves will ALWAYS line up. ALWAYS.
The only way to change the orientation of the halves is with shims, which are problematic in and of themselves.
I’m not saying all tuning is a lie (OK, my title says that, but it’s just me being sensationalist). If your yoyo is sensitive to the relative “depth” of the axle into each half, you might find a difference… especially with wide thread zones that leave plenty of travel for the axle. Maybe the teflon tape itself is presenting any sort of mechanical movement within loosely-threaded halves (doubtful). Swapping axles might also work if there are infinitesimal differences in straightness of the axles. I dunno. A lot of smart and honest people have claimed to have tuned their yoyos, and I believe them.
But the idea that you are reorienting halves is straight-up incorrect as a piece of masking tape or a sharpie will quickly tell you.