White Oak Trouble

[sawwood]

I am making base molding for a customer and using his oak. We cut and air dried them then used our solar kiln
to finish them. Its been two years that the oak has been under cover and i checked the moisture and its a 9%.

We planed all his lumber down to 12/16 for the molding and was ready to rip them to right widths. Now the trouble
starts, when ripping the lumber curls in pinching the blade. The lumber is all riff saw lumber and as i said dried
in a solar kiln.  What has caused this to happen ? Now some of the lumber is corked and not sure i can use it.

Sawwood 

[btulloh]

That tree had stress in it.  Has nothing to do with your kiln work.  Did you saw the lumber?  The boards probably showed movement from stress when they were sawed off the cant I'm guessing.  I worked with lumber for a long time before I started sawing.  If a board showed stress movement when I ripped it, it would continue to do that for every rip.  On short stuff I could re-joint maybe and save a board, but not much can be done.  Maybe someone else will chime in with a better prognosis.

[GeneWengert-WoodDoc]

Saw pinching is indeed caused by stress. 

The stress can be from the tree.  It is called growth stress and will warp the lumber somewhat when green.  Saw pinching after drying is common.

During drying, the wood near the center of the tree shrinks, or tries to shrink.  If prevented from shrinking as much as it wants, means that stress develops and this stress will cause saw pinch when quartersawn pieces are ripped.  Note that most of the time, one edge of qsawn lumber will be close to the pith or center, while the other edge is close to the bark.  This causes side bend when drying and saw pinching after drying.

Do the warped pieces straighten over the next day or two?  If so, then it is moisture gradient related.