I have fabricated sphere turning tools for the different lathes that I use in my shop and made a few more for other wood turners I know. Depending on the wood you want to use and the size of spheres you want to make will have an impact on the tool you want to own. For smaller spheres any of the sphere jigs will work fine, if you want to turn larger spheres you want a heavier frame that holds the cutting tool solid to prevent tool chatter if you are cutting hard woods. I mostly turn pine wood spheres used for mold making purposes which turns easy compared to hard wood species. I recently made another jig using Delrin rounds for the main support base that holds the pivot bearings and used aluminum flat bar for the swing arm and aluminum round stock for the upright cutter base, and a Chinese import carbide cutter mounted on a 1/2 inch bar for the cutter. These tools are easy to make, you just need to end up with a proper elevation for the carbide cutter that matches your lathe center height.