Pine board composition.

[u/CtrayX]

Learning to hand cut dovetails. Been a long week. Why are the insides of some of these big box pine boards like this? Some are solid and compact like the bottom board with the tails. Some are loose and falling apart like the top board with the pins. Why is this happening? Is it the board or me?

[u/No_BetterName]

I’ll add that it’s not your technique. As others have said, pine sometimes tears easier than it cuts. Chisels have to be razor sharp to minimize tear out and some woodworkers even have a set of chisels with a 17 degree bevel angle for softwoods like this. The lower bevel angle helps but doesn’t always eliminate it completely. Less chopping work and more slicing “handwork” with the chisel in narrow passes as you approach your line also helps. Good luck.

[u/Fastco → u/No_BetterName]

While I do think pine definitely can tear, I do think it's a technique issue still. It's probably a combination of sharpening technique and taking too large of bites with the chisel as you approach your layout line. I keep my chisels around 30 degrees and have no problem chopping the tails on white pine with (mostly) no tearing like this. That said I don't this really matters that much as long as the edges of the cut are crisp