Ok, here goes. My son got me into yo-yos and being a machinist I wanted to make an aluminum yo-yo of my own. As it turns out they are considered pretty good playing yo-yos by many people so it has turned into a side business for me. I sell about 800-1000 a year through different online stores in 6 different countries. They retail around $100 dollars each. I sponsor a few kids around the country that compete in contests and such. Here is a video that one of them made using one of my older models.
http://vimeo.com/3736468As for the machining, the yo-yo is actually 2 halves with a bearing in between and an axle holding it together. All the tools are standard carbide tools from Iscar or Kennemetal. It takes 6 tools to make each half. I use Mastercam to program and Solidworks to design. I just make the prototypes myself and I source the production to local machine shops and anodizers. Here is a section view of the assembly. I'll try to post some screenshots of the toolpaths in Mastercam later when I have more time.
-Doug