Open Segment vessels are similar to closed segment except the segments don't touch. They have open space between them. This makes it easier because saw cutting the segments doesn't have to be as accurate and it uses less wood.
How It Works: There are 4 parts to the Open Segment Jig, OSJ for short. 1. Index assembly 2. Indicator and locking assembly 3. Platform assembly 4. Software.
The Index assembly consist of index plate and hub that screws on to the spindle (the hub part is custom made for each lathe). On the index plate are lines used to space the segments an equal distance apart. There are 4 spacing options on the index plate: 30 (for a 15 segment ring) 32 (16 segment ring) 48 (24 segment ring) and 50 (25 segment ring).
The Indicator and Locking assembly is secured to the lathe bed and used to indicate the lines on the index plate and lock the plate in position to prevent rotation during placement of the segments.
The Platform assembly is secured to the lathe bed and used to place and hold the segments. There is a measuring scale built into the platform that allows you to accurately place the segments at a specified distance from the center line of the lathe (radius/diameter of the segment ring) and a spring loaded clamp that holds the segment in place while the glue sets (using Tight-Bond II about 1/2 min.).
The Software ( Excel or other software ), will calculate all the dimensions needed to cut the segments and calculate the total length of board needed for each segment ring.
Please note: You will need Excel 97 and Windows 98se or higher.
The procedure in a nut shell: I design my vessel using 1/2 x 1/2 graph paper and take all numbers I get from that (radius, number of rings and how many segments in each ring) and plug them into Excel or other software, take that info. and cut my segments with a table or miter saw.
Screw a piece of MDF to a small face plate and turn it round. Glue a piece of hard wood to the MDF (this will be your base for the vessel) and true it up. Remove the face plate and install the index plate on the spindle. Screw the face plate back on the spindle, setup rest of the jig and glue on the segments. When you finish all the rings and all the glue is dry, remove vessel and face plate, remove index plate and the rest of jig, screw vessel back on spindle and finish shaping, sanding and polishing etc. and part it off. That's It. I hope this answers some if not all of your questions. The OSJ comes with a complete set of detailed instructions and lots of pictures on a CD.