I can actually fully answer the axle thing⌠there are a lot of âsorta answersâ in the thread so far so Iâll fill in the gaps.
Tapping is not a process that is as precise as youâd think. Because the hole is drilled and then a tap is run down it, a tiny little variation in the hole, a variation in the condition of the end of the tap, the actual tap used and the shape of the tip, how the tap happens to catch in the hole, etc⌠can all vary the end condition of the hole. That means the thread may not end cleanly, or that it may be a tiny fraction longer/shorter than desired.
So, if you sized axles to fill the holes -exactly- then youâd very often end up with axles that were off⌠either the yoyo would close properly, or you may end up with an axle that snags in the bottom of a âbadâ hole and is torqued off center slightly. There is a tiny bit of âplayâ built into threads⌠youâll notice most axles will jiggle just the very tiniest bit in the thread. This is done to prevent the axle from seizing against the metal, or cross threading from sloppy assembly. The more you thread the axle in, the more it centers itself and that goes away, but if you slam it into the base of the hole, and that hole isnât perfectly finished, it can possibly end up not being all that straight.
Is it possible to get every single hole absolutely perfect? yes⌠but itâs also exceptionally expensive.
Itâs -far- easier to just make the hole longer than necessary and solve the problem entirely.
Are there any downsides? not really.
The only potential downside is that it allows space for people to over-tighten their yoyos⌠thatâs about it.
Any notion that the axle being slightly more on one side than the other causes imbalances is purely nonsense. Let me say that again, itâs a total load of crap. Youâre talking about moving a small fraction of a gram from one side to another, directly along the axis of rotation, in the absolute most stable region of the yoyo⌠itâs not going to do a damn thing to induce vibration.
That particular misconception came from the whole âtuningâ movement, which was necessary when some companies started putting out very expensive yoyos with very questionable quality. Moving the axle around in the threads did impact how much vibration the yoyos had, and some people jumped to the conclusion that this was because of the axle shifting back and forth. In reality, as somebody has mentioned in this thread, itâs because it changed the alignment of the halves in relation to one another⌠and since the halves were pretty poorly made, you could try and balance them out and align them better.
So quite simply, the reason there are longer threads than the axle length, is because why bother doing it any other way?
Kyle