kirsten kone and Reverse turning
As you might imagine, reverse turning the bottom of a thin-walled vessel like the manzanita burl piece above can be a challenge . . . but the Kirsten Kone, developed by Oskar Kirsten out in San Diego, greatly simplifies the flexure problem. And they're easy enough to make. My friend Kim Blatt made the one below for me.
Reverse Turning Hollow forms minus a kirsten kone
I have more pictures to post of the reverse turning process without using the Kirsten Kone. While I lie the tool, most of my forms are turned out of holes much to small to accommodate the Kone. There's more than one way to reverse turn . . . I generally do so one of two ways either (1) using a custom made jam chuck or drum chuck (minus the vacuum setup) or (b) using a drum chuck with vacuum setup . . . In either case, the trick is getting the piece centered.