Join Date: Jan 2011
Location: Jacksonville, NC
No hard and fast rules apply to MC and finish turning. MC can change while rough turning, in storage, finish turning, after finish applied due to relative humidity.
Factors affecting MC:
Average annual relative humidity for your area
Species of wood
Open or closed grain wood and ratio of sap to heartwood
Thickness and to some extent diameter of blank
Size of bowl or spindle blank and what part of tree wood comes from base, limbs, crotch, and burl
You can rough turn some species of wood having MC above 30% and finish turn two months later. Am finish turning Yellow Poplar, storm damage from hurricane Irene. Also finishing Crape Myrtle bowl harvested last Feb.
Finish turning too soon may or may not be dealing with lots of torn end grain no matter how many times you sharpen your tools. Again, that goes back to species of wood.