Quote Originally Posted by Derek Cohen View Post
I wonder what advantage there is with a smoother having a bed angle above 45 degrees if it uses a double iron? A lower cutting angle should produce a clearer finish. Bearing in mind that the lower the bed, and the more interlocked the grain, the greater commitment there must be to use the chipbreaker to control tearout.

Two views of a 50 degree bed: for one building a plane for others, it offers a range of choices (i.e. to use chipbreaker, or not). On the other hand, if the plane is for oneself, the choice of the 50 degree bed angle is wishy-washy (sitting on the fence, so to speak). When I chose the frogs to keep in my Veritas Custom planes, they were 40 degrees (#7) and 42 degrees (#4). This was a commitment to using the chipbreaker.

Regards from Perth

Derek
I don't think it's an either-or thing. Close-set cap irons and high bed angles mitigate tearout in slightly different way. I've seen pathological cases where I get small-scale tearout even with the cap iron set back by <8 mils (<0.2 mm). In those cases further increasing the bed angle helps.

I suspect that what may be happening in those instances is that the fiber-to-fiber bonds in the wood are so week in relation to the stiffness of the fibers that even a very short setback creates enough leverage to tear the shaving out ahead of the blade. High cutting angles address this by "breaking" the shaving (converting it to type 2) at the point of the cut instead of several mils up the blade back. The downside to that is of course that finish quality is compromised a bit.