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Looking for input from those mechanical/engineering minds

You’re missing the point. The stationary sanding disc/board/block is to span the width of the segment ring. This assures squareness. And all segments are subjected to same treatment, unlike a stationary segment ring against a rotating disc.

Tim
 
Tim Hunter said:
Simple. The work piece can be held out-of-perpendicular to a sanding disc, resulting in non-uniform segment thickness. In contrast if the work piece is spinning about it’s centerline, all segments are exposed to the same net force of a stationary sanding disc/block/board.

Tim
Click to expand...
Uhm no. I don’t think so.
 
David Stranz said:
OK, that makes sense so long as the sanding board remains perpendicular to the face. If not, then you're sanding at an angle and you'll end up with segments tapered either inward or outward. It would seem to be a bit harder to do that if the vessel were face down on a rotating disc where all segments were simultaneously in contact with the disc. Potatoes, potahtoes in any case.
Click to expand...
True. however, it is FAR easier to manually hold a surface flat to a spinning disk than it is to hold a spinning disk flat to a non-moving surface. So long as your pressure (which should really be very little) to hold the surface to spinning sanding disk is even. (if held near center and the surface is spread out further than center, it becomes easier and easier the bigger the surface gets)

Similar problem with the surface planer tool I initially posted way back near the start , if you have the base of a cone shape needing to be flattened, it becomes more difficult to maintain a parallel orientation (unless you rig some sort of steady rest feed that acts on outer rim of the cone) to the cutters... (By the way to those who mentioned it being an open segmented ring, I tried and found that the Stewmac drill press planer actually does work very neatly on things like that where a regular lunchbox planer would have shattered the piece to smithereens so long as you can keep the piece flat and stable as it is fed into the cutterhead - if the pieces are well glued and whole (but then if that thing would break the segment, so would turning it on a lathe)
 
Tim Hunter said:
You guys don’t understand geometry of machining.

Spin a vessel on your lathe, hold a sanding disc to the end, and show me how you sand one side of the vessel lower than the other…you can’t.
Tim
Click to expand...
doesn't help to get the first surface trued flat before gluing the segment ring to the vessel... which is the problem I think we're talking about. :)
 
Wow, this has taken a turn from my original post!

For the record: I turn my segmented vessel on the lathe and hold a board with sandpaper to it to flatten it out. *Keep in mind we are talking about a very little amount of sanding.

This is how I have done it from the start; I have never had a problem; it is smoother sanding this way for me and I do not want to change.

Others may do it differently
 
Yeah, look what you started Jim haha. I use both methods extensively on about everything I make - and they are both good. Both methods have their idiosyncrasies though. You can create poor geometry either way, you can also create good glueing surfaces either way. The devil is in the details.
 
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