Peter T":3lxmejfg said:
What are the chances of getting the frog so accurately aligned with the back of the mouth that the iron is actually touching, and supported by, both the frog and the back of the mouth at the same time??
Very slim IMHO.
If the frog is set a few microns too far forward, then the iron won't touch the back of the mouth, and won't be supported by it.
If the frog is set a few microns too far back, then the iron will be lifted off the from by the protruding back of the mouth.
The "Safe, default position" may be a nice idea, but one that is virtually impossible to achieve!
Did you ever try it out yourself? It really works, the plane becomes more solid and less chattery. Feeling with your fingers to get frog and sole even is "good enough".
In your theory you forgot one practical problem: The blade is not flat when the chipbreaker screw is tightened. It is bowed quite considerably. That means (theoretically) only a very thin line where the blade meets the frog or the sole really makes solid contact. In practice the blade bows up and down under planing pressure. When the fulcrum point is lower, less force is vailable for this bowing thus improving the situation.
woodbrains":3lxmejfg said:
We have different sorts of planes for rough and fine work, to expedite the process, setting the mouth wide has no bearing on the speed we can plane. If , as David C states, the thickest shaving is about 6 thou, then a mouth setting of 7 thou would be ample, in say a jack. Then when fine tools are used, we do not have horrendous tear out to deal with, which will inevitably take us longer in the end.
That's not how I use and set a plane. I am not thinking beforehand: "this board needs a 6 thou shaving so let me set the mouth at 7 thou". No, I set the plane by feel. In a jack plane, as thick a shaving as I can push comfortably, maybe changing it when I get tired, or when I hit a particular hard patch. The jackplane is often used across the board (when not using electrical jointers) with a camber, both helping to reduce the tearout. Also the chipbreaker is set as close to the edge as possible on that cambered blade, further helping to reduce tearout as much as possible. You won't completly avoid tearout when using a jackplane, that's the smoothers job.
Let me conclude with saying: set your plane however you like and enjoy using it. Keep an open mind to the ideas from others. And discussion forums are meant to be fun, so don't take anything too seriously.