Rick Cook wrote:

Duane Bozarth wrote:
Stephen M wrote:
...

Hidden in all of that is the false assumption that the presurfaced stock is
actuallly flat and straight when you buy it. It's probably pretty flat when
they mill it, but it probably has plenty opportunity to "move" after
milling. By definition, you de not get to acclimate your stock before
milling, because it's milled in someone else's shop.


But that's a different operation (resurfacing)...if the two surfaces are
parallel, they'll remain so within the differential expansion of one
portion of the same board wrt to another which is going to be quite
small...

Not in Arizona.
Given the radical changes in humidity between here and where that stock
was originally thicknessed, it has a nasty tendency to bow, warp, cup, etc.

You can work around this, but you need to choose your wood carefully if
you don't have a planer.

I still say the two surfaces will be (essentially) parallel to each
other...

They may not still lie in a flat plane, but that's a different issue as
I've noted before. In that circumstance certainly one would have to
resurface and all that--I never claimed otherwise.