I just finished reading thru Lyle Jamison's newsletter about how to work with a collars on the opening of a vessel and then adding a finial on the top of that. I agree with his comment that Cindy Drozda is a master at the finial stuff.
Anyway, regarding how to approach collars and finials he suggested:
First option was to rough out and let dry and then return it to keep the opening from warping or distorting - like he said there are difficulties in working with dried out wood..... not my choice nor what I do either
Second was finish the entire vessel and go back and true up the opening when dry. You can then create a ledge also after truing up the opening.......... To me------that does not seem to be a very good method because you could easily mess up the opening. Or if it warps upward on you then there may not be enough wood/stability to trim down again to get rid of the distortion. I suppose you could leave the rim area a bit thicker to take some of the second cutting into consideration............
Third was to cut to final thickness and let dry then cut the collar a bit larger in diameter to hide the distortion in the opening but this does not account for upward warping on the top of the vessel unless you turned it thick on the top to give yourself extra material for a second returning of the top portion.
I try alot of different approaches (including the above 2nd and 3rd)to keeping the opening true as possible......I have sprayed some MS on the rim and used my compressed air nozzle to spray it into the wood-like blowing it into the pores to displace any moisture in there....and then using
CA on the rim inside and out about 1/2" and it works with some woods.
Anybody else game to suggest other ways ????