Axle is a part of the yoyo which connects the two halves. It holds the yoyo together and is a vital part of your yoyo. Most yoyos have it they can (basically) take two forms (and plenty of sizes):
First, silver option (left) is a HEX bolt with a nut on the other side. This is most commonly used in plastic, affordable yoyos. Both ends with the hexagonal shape fit into a moulded section of the yoyo and hold the axle / nut in place. You can then screw & unscrew the yoyo.
Second, black version (right) is mostly used in metal yoyos and advanced plastics. The thread is made into the actuall yoyo half and the axle screws into it. That makes the yoyo very smooth and relatively easy to produce. However this option is not replaceable which means that once (if) you wear out the thread you can throw your yoyo away.
Stripping the thread
Very common problem for begginers is stripping the thread itself. That hapens if the player continues to screw / unscrew the yoyo all the time, even when not necessary or required. You should really open your yoyo only for maintenance. The second most commonest way to strip the thread is applying too much force while screwing the yoyo together. Once you can feel an obvious resistance from the yoyo, don’t screw any harder. Just leave it be and play! Warranty does not apply to stripped threads / axles.
How can i avoid stripping the thread / axle?
Do not open the yoyo unles it’s absolutely necessary. You should really open your yoyo only for maintenance. If you make a knot in the middle of the yoyo, just use your keys, pen or a safety pin to get the string out of there. Putting the string on the yoyo is also possible without taking it apart. Not only possible but actually easier because you don’t have to be super_precise. Just unwind the end of the string, make a loop and put the yoyo in there. While performing maintenance (replacing pads, cleaning the bearing) use caution to unscrew / screw the yoyo together. Yoyos are designed to be taken apart but if you overdo-it they’ll break.
i already my friend broke my yoyo! Now what?
Depends on what kind of axle you have. If you have the HEX nut it’s very simple. Just buy a replacement one (either form us or from your local hardware store) and change it. Just make sure not to loose any of the parts from the yoyo while you do that.
If you have a (metal) yoyo with black, small axle than you have basically two options, neither of which has to work. Try fiddling with your axle, put it in the other half of the yoyo or try to put in an axle which is a bit longer. It might hold on the remaining threads you (i mean your friend) didn’t strip. Or try finding someone with a Screw Tap, they might be able to screw in a size larger axle and save your yoyo.
Neither of your “great” advice works! Now what?
Well not you’re out of options. Technicaly you can try finding someone with the same problem and buy his “healthy” half from him. Or you have a really nice paper weight.