The axle on modern YoYos is usually a threaded metal rod that is screwed into each side of the YoYo. Then bearing then sits on this axel.
With repeated use the thread on the axle can get stripped (ie. damaged) causing the YoYo sides to keep coming loose, and sometimes come apart altogether during use! (not good!)
If you're finding it hard to tighten your YoYo, check the thread on your YoYo and make sure it hasn't been stripped. If so, it's time to buy another axle.
Browse our collection of axles below!