Step 1: Prepare a Piece of Wood
I started with a piece of wood 9" by 3 1/2" I mounted it on the lathe between centers, and used a roughing gouge to bring it down to a 3" diameter. Then I used a Easy Wood Rougher to make a tenon on one end. The tenon is 2 1/4" by 3/4" to fit in my chuck.
Step 2: Rough Shaping the Sphere
After remounting the piece back on the lathe using the chuck, I used a spindle gouge to shape the sphere. It's easier to give the sphere it's basic shape before using the jig to refine it.
Step 3: Final Shape
I used the EZ sphere jig to give the sphere it's final shape. This jig mounts in your banjo using the tool post hole. Set the cutter in the center of the sphere and rock it back and forth. The depth knob is on the top of the jig, and you need to give this a full turn after each pass. I brought the sphere down to a final size of 2 3/4"
Step 4: Button Hole
After removing the EZ sphere jig I drilled a 1" hole 1/2" deep for the button. I used a jacobs chuck mounted in the tailstock, and a forstner bit.
Step 5: Remove the Sphere
I used a 1/8" Parting tool to part off the sphere form the remaining wood.
Step 6: Making the Button
With the remaining wood still in the chuck, I made the button using a parting tool. The button is 3/4" by 3/8" I brought the diameter down checking it with vernier calipers. After shaping and sanding, part off with a 1/8" parting tool.
Step 7: Cutting the Groove
I mounted the sphere in a vacuum chuck to sand and cut the groove. I marked the sphere with a pencil, this will give me a reference line once the lathe is turned on. I used a 1/4" parting tool to cut the groove, (make sure you bring up the tailstock to help support it.) I cut the groove about 3/8", although in hindsight this was a bit much. If I did it again 1/8" is probably enough. After cutting the groove do your final sanding up to 600 grit.
Step 8: Painting
My wife Robin painted the PokeBall with acrylic paint. First the black then the white then the red.
Step 9: Optional
Dressing up your dog as Beedrill (or whatever costume you have) is optional, but I think it's the best part :)
I hope you enjoyed this Instructable! I had a lot of fun putting it together. If you make this project, please share pictures in the comments.