I’m still having a ball turning spheres! This is how I turned a hollow sphere. I first mounted a piece of wood about 3 1/2″ square by 5 1/2″ long between centers and turned it round with tenons either side sized to fit my jaw chuck. I measured the diameter of the cylinder at the center point and it was 3 1/4″. I then parted the cylinder in half.
You can click on any of the images to see a larger version.
Given the outside diameter of the cylinder at 3 1/4″ I decided to make the internal diameter of the sphere 3″. In order to create a template to use while hollowing the sphere I cut a 3 1/4″ x 3 1/4″ piece of hardboard and attached it with double sided tape to a piece of scrap held in a chuck. Using a parting tool I made a 3″ circle from the hardboard. I also drew lines through the center of the hardboard.
I mounted one half of the cylinder in my jaw chuck and using a spindle gouge and a round nose scraper I hollowed it out, checking frequently with the template to make sure I was hollowing half a sphere. I also turned a tenon on the end. Then I sanded the inside.
I repeated this with the other half of the cylinder, except I turned a mortise on the end. I established the diameter of the mortise first, sneaking up and performing many test fits with the other half of the cylinder. Once the diameter was established, I established the depth until the two halves fit together nicely.
After bringing up the tail stock, I then proceeded turn the outside of the sphere. For details on turning a sphere please click here.
Before I removed the sphere from between centers and mounted it in the cup centers I taped the two halves together.
The finished sphere, not as perfectly round as some I’ve done before, but this one is hollow!