This one is once turned. I haven’t tried twice turning HF’s yet but plan to, especially side grain. The end grain doesn’t seem to move as much as the side grain.
To get an idea how much wood will warp when drying relative to the orientation and where the blank is cut from the tree, look up the species in a chart, or better, in the online Wood Database. For example, look at Black Cherry:
www.wood-database.com
Radial: 3.7%, Tangential: 7.1% Volumetric: 11.5%, T/R Ratio: 1.9
The volumetric shrinkage is important, but tangential and radial shrinkages can make a big difference for predicting face grain turning warping. The tangential shrinkage often about twice that of the radial shrinkage. That causes warp as face grain (flat sawn) turnings dry. One number, the T/R Ratio, puts both of these together. The higher the T/R ratio, the more warpage.
BTW, tangential is tangent to the rings, looking at the end grain of a cross-cut log section. Radial is across the radius of the log, or to minimize juvenile wood effects, from the pith out towards the bark.
For comparison look at the volumetric shrinkage and T/R ratios of Black Mesquite and Red Oak
www.wood-database.com
Radial: 2.6%, Tangential: 3.5%, Volumetric: 8.5%, T/R Ratio: 1.3
www.wood-database.com
Radial: 4%, Tangential: 8.6% Volumetric: 13.7%, T/R Ratio: 2.2
So a face (side) grain blank turning might warp far more than an end grain turning. (All this is the reason that quarter-sawn boards are more stable that flat-sawn boards when working with flat wood.)
This is just an average for samples tested - the actual T/R ratio varies with the specific tree, where the blank is cut from the tree, and the proximity to the pith on one side, or worse, reaction wood. Shrinkage along the grain, the longitudinal shrinkage, is usually so small it can be ignored.
If interested, this Wood Database article might be useful:
www.wood-database.com
Note from this article the seasonal stability is not necessarily related to the wet-to-dry shrinkage.
The T/R ratio is the reason lidded boxes are often made from end grain blanks so the lid is less likely to stick. My solution to things with lids, such as Beads of Courage boxes, where it is sometimes impractical to avoid turning side grain, is to make tapers on both lid and vessel.
There is far more to the story. The best book I’ve found about wood, how it dries, how it shrinks and far more is
Understanding Wood by R. Bruce Hoadley. Unlike some practically unreadable technical writings, Hoadley is both a craftsman and a wood technologist and explains things on our level! I keep an extra copy of the book on hand to lend to those who show an interest.
Sorry for the “blog”; hoping this might be useful to some.
JKJ