Any tips on how to fix a stripped axle?
Epoxy the axle into the bad half and hope for the best
Happened to me on my first all metal yoyo, the Shutter. I brought another one. $40 wasn’t worth the trouble of trying to fix it but if it happened to one of my more expensive throws, I’d love to know how to fix it… if possible but it sounds like what @SlowThrow mentioned above is likely your best bet unless you were to send it of to get re-threaded but in that case it may be as expensive as buying a new one.
axles are $2 just get a new one
Typically axles are steel, yo-yos are aluminum, axles always win the crossthreading battle. That’s not to say that an axle can’t be damaged, I’ve seen it myself, but it will not be from the aluminum, it’s usually tool marks from pliers. They can also bend from impacts, but if it’s stripped, the aluminum gave out.
There are thread repair kits, but there is so little material in a bearing seat that I don’t think it ia a feasible repair, and for sure would be a real challenge for someone with limited mechanical ability or knowledge. I would strongly advise against a first experience with thread repair being an attempt at M8 sized threads into a blind aluminum hole
What yoyo was it? If it was a magic yoyo, or a yoyo that can take a half spec c bearing, and you were using the short axle, the long axle can sometimes be threaded into it a little farther than where it was stripped. I’ve done this for a few myy k2s that were overtightened by my students, and I did it to my own shooting star. ( I learned axle length is really important when you have a yoyo that can take half spec bearings.) It does make it unresponsive only, as the axle width requires a full sized C bearing. If you’re lucky, and the axle can be received by the stripped side still, the yoyo won’t have much/if any vibe from this. It is a weak point and it may strip again in the future.
edit to add Kyle is totally right about how steel will win the cross threading over the yoyo. If you can do what I described, be really careful to clean out the axle hole, and when threading in the axle, it should thread in with no resistance. If it stops, or takes force, it is not in the original threads and it needs to be taken out and re threaded in. Lightly use an allen key, but do not use force, it should go in easier than unscrewing an axle that is stuck in another half.