The first step on making this was the design. I will illustrate multiple steps I went trough, and how and why I did them.
I took student membership at Techshop (www.techshop.ws), so I can use the facilities. I took a SBU for wood lathe and went to work. I got some personal tools for advanced hollowing.
Step 1: Design
Segmented vase is made by putting together pieces of wood, to make a rings, stack the rings, and then turn them on the lathe. Hollowing becomes easier, but the design is constrained after you start.
The design is first created as a half section. This is the shape of the vase or bowl you have in mind. I roughly used the thickness and the width, I will need to have sufficient overlap between layers. I decided to make each rings with 12 segments (each segment is a regular trapezium, with an included angle of 30 degrees). I tested my math skills, and just to be sure, by cutting some foam core and putting them into a ring.
I made the a CAD file (this can be done on paper with a ruler and pen too) and took a 1:1 print of the segments i have to cut and number of segments i have to cut.
Step 2: Buying Wood and Prepartions for Cutting Segments
I planned one face on a planner and cut to equal widths of 1 inch on a table saw. The idea was to cut them into segments on a miter saw. I can set the miter saw to cut a 15 degree angle and keep flipping as I cut to get a consistent length and angle for all segments.
I test cut some pieces to see how the miter saw performs and to check its accuracy. Its hard to control accuracy of a equipment used by everyone or use a jig for long duration which the project calls for (you can cut everything at once, but loose out on the liberty of correcting for errors as you go).
Easier tests like cutting three pieces and measuring for 90 degrees on a square is good first check.
Step 3: Making of a Jig to Cut Segments
So I set about making a jig to cut segments. The important thing is to realize that not everything about the segments need to be accurate. Some dimensions need precision and then some need just consistency. Putting your efforts in the right direction is important. For example, Having an exact angle is important. If you err, more than a tenth of a degree, the ring will have gaps(either on the inside or outside, depending on the error). The length of the segment on the other-hand, need not be accurate, but consistent. A change in length, will only change the size of the ring slightly.
The jig is a simple one. It has a stopper, a MDF backing to hold everything together and to avoid burrs from exiting blade. Later version have a hold-down clamp too.
To check the jig, I cut some scrap wood and check the roundness of the rings. which turned out pretty good. This is followed by cutting all the segments, labeling them and making sure everything has couple of spare segments.
Step 4: Glueing the Segments
I started by making them into pairs. The glue i used is titebond. The curing time is just about right. and its water soluble, gives a very good bond too. I used the sliding method of gluing to avoid air gaps and used more glue than required. Rubber bands were used as clamps to hold them together. Once the pairs are dry, i glued them into half rings and made a fast jig to ease the process of using rubber bands as clamps. Now, with later learning, i feel hose clamps are a better alternative when making bigger rings.
It doesn't take long for the glue to cure considerably. You can remove the rubber band in about 30-60mins depending on the temperature you are working in.
Once the rings are all done, Major chunk of the work is done. You can start to look forward to the turning on the lathe.
Step 5: Planning, Glueing and Stacking the Rings
Sanding disk: easy on small rings.
drum sanding: did not try this. Dont have one. Can try the planing machine may be.
lathe: very good for big rings. Use hot glue gun and stick the ring to a plain piece of MDF. Use a old scrapper and remove the first layer which would be mostly glue and just unevenness. The next level of accuracy is needs a bit of work and dealing with safety hazards. I pasted sanding paper on a board and put my weight on the ring. It really flattened it perfectly. A good way to check is with a ruler. Lay it diagonally over the ring and check for flatness. Now, flip the ring and flatten again(this can be avoided as you stack up and you have two chucks/mounting plates).
Use glue and stick rings with each other, one after another. You can also use the tail stock of the lathe for clamping pressure. as you stick rings, its easier to remove bulk of the material from the inside. You can do this later, if you have the right hollowing tools.
Step 6: Glueing the Two Halfs
You can begin to use # 60 or #80 grit sandpaper to smooth the curves. Once the shape is close, start using progressively finer sandpaper grits up-to about #320 or #400.
Step 7: Finishing
After some 80-100 hours of work, you will have a beautiful vase to show for the joy you had in making it!