I’m not sure it would have to be so rare, because it may be altering an angle (ie the degree of parallelization of the two yoyo halves) rather than a distance. Altering an angle would have a more pronounced effect on the yoyo rims vs one another, therefore having a more dramatic effect on the vibe.
Ah, I see now! Could be, could be. Certainly a plausible theory!
^^Altering the angle was what I was trying to convey in my last post.
Check out the distance between threads on this:
Definitely a lot of wiggle room, especially with threads in the yoyo halves that are too big, which was indeed the case on a number of old yoyos that folks tended to tune. And with teflon in the mix, that might be what’s allowing the halves to end up angled different against the bearing.
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Yeah sorry I had missed that you’d suggested that. My apologies. 
Yoyos from this era had a subtle but HUGE design difference: no bearing post. The axle is wide because it is acting as the bearing post. The bearing post is what aligns the half and what generally determines smoothness/vibe is the fit of the bearing post to the inside diameter of the bearing. Those axles are WAY smaller than the inside diameter of the bearing and that is why those yoyos vibe. The effect of the teflon tape is to increase the fit of the axle to the inside of the bearing; it doesn’t do anything in the threads - this is widely misunderstood. It’s true that aligning halves can do some amount of fine tuning (the more error in the halves, the more this works) but generally the thing that affects vibe the most is the fit of the bearing post.
Those axles are undersized by .005". For modern yoyos with bearing post we shoot for about .0002" under the size of the inner diameter of the bearing. In machining terms this is a massive difference. If we made a yoyo with a bearing post .005" too small, it would vibe just like those old yoyos.
Hi Da5id, thanks for the helpful response. While I understand what you are saying, does the number of threads per inch and precision of the threading not change the alignment of the halves at all? In my line of work, I frequently use higher TPIs to increase the precision of screw positions/angles - typically finishing with TPIs of around 100-150. This is much more precise than lower TPIs. However I also understand that the bearing seats these days may predominantly control alignment of the axle - I’m just surprised there is no effect.
The purpose of the threads is to fasten to the halves, and not to align. Accuracy of the threads doesn’t matter. The only time the axle can cause vibe is if it is bottomed out in a blind tap hole. It’s just in the design - bearing post is the key.
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If this is true then there can be no way to tune modern yoyos, making the title not so sensational after all.
This is a very thoughtful discussion all around.
Thanks, guys.
from my experience the yoyo can be vibe free and then you change the axle placement and it makes it have vibe. that’s without teflon tape. then you change it again and it makes it dead smooth. in most of my yoyos the floating method works the best. with the axle just in roughly the middle. I have no idea why this changes anything and it perplexes me too. some of my yoyoys are smoothest with the axle all the way in one side.
Great thread! Everything we’ve been told is a lie.
Im thinking tighter specs on things like parallelism (of the two halves and bearing seats) and perpendicularity (bearing post and axle with respect to each half), the less felt vibe. Runout should play a roll as well. I’ve never seen a complete drawing of a yoyo, could someone post one?
I’ve seen dings on two halves go “out of alignment”, could this be due to a coeffecient of thermal expansion mismatch between steel and aluminum? Worn threads? Torque applied? Which side the axel was screwd into?
I’ve also balanced two halves down to a milligram on a beater I have and that did not reduce vibe any. With that said, I dont think lateral movement of the axel would change much. SOMETHING changes when you tune a yoyo but what?
Try this at home!
Take any metal yo-yo. (I guess any yoyo really, but we’re talking about metal in this thread).
Screw it together, make sure it’s tight.
Take a pencil, mark a line across the gap onto both sides… this gives you an exact reference point for how the halves are aligned.
Unscrew the yo-yo.
Move the axle around a bit, in/out, etc… maybe bottom it out in one side so you know it has moved.
Screw the yo-yo back together.
Check the lines… do they line up?
Evaluate your position in this thread based on the results.
Kyle
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Clearly Kyo is right, empirical data is always the way to go, but I don’t think anyone in this thread was really taking a stand one way or another we’re just trying to work out why things are the way they are. I have some throws that attempted tuning makes absolutely no difference with, and some that do. I’d just love to understand why. Plus, with manufacturers commenting in a thread like this, which is fantastic by the way, us mere mortals have to try and take on board what they say as they have a very different but very important perspective on the whole process. Now if two different designers/manufacturers have different points of view…
Heh, I was taking a stand. 
The thread was prompted by doing exactly what Kyo said to do.
However… I do need to reiterate that the more detailed version of my stand is “you cannot reorient halves to one-another just be changing the depth of the screw in either side”. There may or may not be other ways to tune, but I think that the relative weight change from the axle shift isn’t likely to do much either.
There’s always one
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I’ll get this out of the way up front… the weight shift is absolutely insignificant. It’s shifting fractions of a gram from one side to another, at the most ineffective point you could possibly choose.
Now, to the alignment issue. The yo-yo linked below has a fixed gap and a metal bearing seat… there is no ‘give’ to where it stops turning. The axle isn’t large, #8-32 I believe, and the threads are tightly machined… so it’s not a thread pitch issue.
There really is no question that adjusting the axle can change the alignment of the yo-yo halves. Drastically? no, but enough to make a difference* (see note below)
Now… how much impact on the actual yo-yo performance? in a well-machined yo-yo, none. (assuming the axle doesn’t bottom out in a poorly tapped hole, which can cause it to shift out of alignment, or possibly just prevent the halves from aligning on the sides of the bearing).
If the bearing seat is tight, ultimately the halves should slam against the sides of the bearing, and do so flat.
- The only time changing the half alignment would make a difference, is if there is a run-out or balance issue within the individual halves. If that’s the case, it’s about poorly made products more so than some random axle problem.
Kyle
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Kyo, we’re of the same opinion here, but I’m still even stricter about it than you, I think.
Your photographic evidence shows a shift has occcurred. I don’t know the reason for it, but my experiments did not. So I could show a set of photos in which the line didn’t change at all. Relative tightness? Bearing not fully down on the seat? I don’t really know how your shift occured, but I had none (probably wouldn’t have started the thread if I saw even a minor shift. ).
In a pure math model, such a shift is impossible, which means that it’s some unpredictable force at play here… again, amount of torque or some sort of weirdness with the axle or shaft. Couldn’t say.
I can replicate this with any yo-yo I’ve tried it on (and I have quite a lot of them). I can do it over and over and get different positions too… many of which will be very similar to one extreme or another, but notably different.
Torque isn’t an issue when you have a ‘solid’ bottom end… the bearing isn’t magically changing size.
“In a pure math model”
…that right there is your problem.
Your model only works in an absolutely perfect, idealized world where both halves are threaded -absolutely identical-, and where the threads on the axle are -absolutely flawless-. That simply isn’t the case. If the threads were flawless, they’d seize up like crazy when trying to move the axle… there -has- to be tolerances involved, it’s a fact of a world with friction.
Now, because this myth has been SO widespread over the years, I’m going to hit this last point again (GregP I know this has nothing to do with the point you’re making, this is to the thread as a whole)
Just to really beat the idea of ‘it shifts the weight’ into the ground for good… one side being heavier than the other DOES NOT cause vibration, period. Don’t believe me? Take two well balanced yo-yos of vastly different weights that have the same axle/bearing size… yyj works well for this since most of theirs are the same guts. Swap halves. Look! no vibe! …just a ton of rapid precession (yo-yo turning in circles).
Kyle
My Gfunk has visible vibe when detuned and is much smoother when tuned. Today, I measured at several points from rim to rim and found a difference of .6mm when detuned and .1mm when tuned.
The axle was straight and rolled across a flat surface with no wobbles but a visual inspection showed the threads were mangled. I’m thinking what “tuning” really does is improve the fit of threads between axle and yoyo halves.
http://img.tapatalk.com/d/14/03/22/ezy3ydug.jpg
I agree that threads and axles aren’t perfect; it’s not a “problem” that I’m talking about the theoretical math; just pointing it out!
I will admit, I’ve never had luck with tuning, and I only tried the “draw a line” test with the one combination of yoyo and axle, and it lined up perfectly the same each time. Could be that on a different yoyo I’d see the same results as you.