The last step is to press the axle into place. You can place the yo-yo string around the axle before you do this to make it a little easier to string up. Align all the pieces in a vise and slowly increase the clamping pressure. The axle should methodically be pressed into the yo-yo discs. Continue until the axle hits the surfaces of the vise -- this should give you the 3/32" (2.5mm) gap that you were looking for. If the gap is too big, you can put a spacer between the yo-yo and the vise and continue tightening the vise until you have achieved the desired gap, but of course, the axle will protrude a little from the disc. If you can twist the yo-yo discs easily with your hands, then the axle is too small. You can try wetting the axle which will cause it to swell and let it dry and try again. After a couple of times with this process, the axle fibers will be resized and you will have to use a new axle, but this won't be too often.

A tight fitting axle can be press fit into the yo-yo sides without glue. If you refrain from using glue, an errant throw can send one or both halves spinning across the room. If and when you glue the axle into place, make sure that you put a drop of glue inside the hole but toward the outside of the yo-yo discs; press the axle into place as described above. The yo-yo may not function well if any glue squeezes out between the two discs because the dried glue may interfere with the string.