There are mainly two ways in which you can cut timbers. One is to cut across the grain, called crosscut, and the other one is to cut along the grain called rip cut. There are specific types of saws for making crosscuts and rip cuts. If you use a wrong saw, you can damage the teeth. You can use crosscut saws for cutting diagonally to the grain.
Woods are made of fibers. It's like a bundle of strings. When you try cutting that bundle, rip cut saws cuts like a chisel along the string. Two cutter knives sticking on right and left and cutting across the string s is a crosscut teeth. You need to understand how handsaw cuts the material in order to properly use both crosscut saw and rip cut saw. Since Japanese saws are pull saw, they cut only when you pull. So please don't put any pressure when you push back the saw. If you put big pressure when you push, you might bend the blade.
Crosscut teeth consists of two teeth in which one points slightly to the right and the other one to the left. The edge of the teeth are very sharp like a cutter knife. Crosscut teeth cuts wood fiber at a certain width. It works the same for when cutting diagonally to the grain. If you use crosscut saws for making rip cut, you cannot make clean and easy cut.
Just like in the diagram on the left, rip tooth also consists of two teeth just like a crosscut teeth. The teeth edge is flat like a chisel, and it carves out the materials as you make strokes. Since rip teeth carves out the material it's cutting, there more saw dust is produced compared to crosscuts. If you use rip cut saw for making crosscuts, you cannot make smooth cuts because the teeth gets stuck on wood fibers.
By putting some rip teeth on crosscut saw, saw dust is more efficiently removed from the cutting surface.
Crosscut teeth with some rip teeth:
L series LH, LG / RAZORSAW ORIKOMI All Purpose, Large Teeth / MEGUMI /
RAZORSAW SELECT 200, 250, 300 Timberman's, Green wood, Pruning, Fruit Tree /
FD-20A All Purpose, 20G Green Wood, 20T Timberman's, 20F Fruit Tree /
RAZORSAW 180 Woodworking / SELECT 200 Garden / Plant Hunter 210, 240, 270 /