Inside-Outside turning is a process in which 2 or more blocks of wood are glued together with craft paper (or newspaper) between each joint so that you can split them apart easily. Then once they are glued, the piece gets turned to a specific shape, sanded and finished. Then the glued up blank is split apart with a chisel and each block is turned 180 deg and permanently glued without the craft paper, re-mounted on the lathe and finish turned.
Follow along and I'll show you how I made this inside-outside vase with maple on my lathe.
Step 1: Gather your materials
I found a nice long stick of maple. I cut 4 blanks 1"x1"x9". These need to be square on all four edges. This required me to cut all sides of the blocks on the table-saw to ensure square.
Step 2: Glue and clamp the blank
Now its time to glue the blank together with craft paper separating all glued surfaces. I found it easiest to take two of the blanks and wrap the paper around 2 adjacent sides. That leaves 2 blanks without paper. glue them together and clamp it up.
It is extremely important to ensure these are glued square. There can be no slipping or sliding. So when you are clamping, place the clamp pads on the separation line squeezing all the blanks centered to one-another. once you have them held in place square, add a couple more clamps to get even pressure across the blank.
Wait about an hour and unclamp the blank. Tear off as much of the paper as you can and scrape any glue off the blank.