Joe shelton
A piece of 1X pine, fresh from Lowes, gave me fits trying to make crosscuts. At first I was using a small circular saw, and the kerf closed down so tightly that the saw stopped. I had to work the opposite end of the board to finish what I needed.

The material was 1 X 12, and I fooled around with it when I could spare the time. A section at least 14 inches of this board will, when cut rip or x cut, close down so hard that none of my handsaws can cut more than four inches into it, and mostly less than that.

I've never seen this before. I've read of case hardening, but I thought that manifested in rips.

What causes this?