Inspired by an old yo-yo, it's an all printable (except the string) bearing style yo-yo.  It can be assembled with the printable M5-0.8 hex head bolt and nut, real versions of the same type, or any combination of them.  https://www.youtube.com/watch?v=OrdY62d68W8Print Settings (printed on an UM2; PLA; 50C bed):-As fast as your printer will print on the yo-yo halves; 80% Infill.-Print the core as slow and as cold as you can at 100 micron to prevent curling; it's a hard print, if it doesn't come out well remember it's the center that really matters; 100% Infill.-Bolt and nut 40 mm/s at 100 micron 190C; 100% Infill.*Printing on a non-heated blue tape bed is preferred as it will create very slightly rounded bottoms on the yo-yo halves meaning less string friction potential. Stuff to know:Twist the two halves together and test action incrementally to get the perfect fit.Use a lock nut if going with the real version, the printable version has its threads stop a bit before the end preventing the bolt from turning any more.  Don't turn the bolt too hard you will crack the nut as in the image above, it's pretty hard to do.  Use petroleum jelly as a lubricator between the core and bolt interface.If using a real bolt, sand the threads down a bit by twisting the bolt through some sand paper; this will prevent the threads from potentially cutting into the plastic.For a permanent device, glue a real lock nut and bolt into their respective cutouts.  It's not recommended to glue the plastic bolt into place as it will break if the yo-yo hits a hard surface at high velocity.