Bill Tindall, over at wood central has gone to great lengths recently to find information about the planing test that was done around 1980 at Yamagata University by two professors that none of us have probably ever heard of, professors Kawai and Kato.
I suspect this video is going to be popping up all over the place as a result of Bill's efforts in general, and you may have seen a link already at wood central to the video posted elsewhere.
What it describes in motion is what is going on below the cut line based on different cutting conditions and different combinations of cap iron projection and effective angles of attack (as well as without them). You have probably seen some pictures from this video, but to see the wood fibers moving in video is a lot more instructive. What it describes in general is that with the cap iron set properly, we're probably not ever going to need anything other than a basic bench plane to plane anything at all. The settings in the video, I think range from .004" from the edge to .012" to the edge (perhaps only .004" and .008" are included).
This is the direct video link to the video at Yamagata University, and if it changes, I will post a link from elsewhere, but this is the best quality of the video I've seen (it's large). Start around 3:00 if you don't want to watch particulars about the machine. This is a direct link, and it will pop up a video screen.
Original Cap Iron Video
And the credit that goes with the video (please do not repost the link to anyone without providing this credit - the video is not public domain):
Educational Video on "Influence of the Cap-iron on Hand Plane."
Created by Professor Yasunori Kawai and Honorary Professor Chutaro
Kato, Faculty of Education, Art and Science, Yamagata University.
Video taken in Yamagata Prefecture, Japan.
There are other ways to control tearout, like
* steeper pitch
* very tight mouth (note the video is done totally without a simulated mouth ahead of the iron, the cutting effect is entirely due to the cap iron and the iron itself)
* sharper iron and thinner shaving
* discretion in picking wood, skewing a plane in a cut across quartered grain,
* planing with the grain regardless of what it takes to do that
But to do what is shown in the video is probably free, and it can be done with very inexpensive planes as well as expensive planes will do anything. No 55 degree frogs are needed, no 3 or 4 thousandth mouths.
Bill's excellent detective work to track this stuff down came with perfect timing, right along with when I was drawing conclusions from playing with an $11 common smoothing plane ($14 if you include the spare iron) vs. one that cost me $300 in materials to make. I still have more to learn from using the cap iron, like when I can back off of it some to improve the surface, but needless to say that when it is set tight, it has still given a better brighter finish than my 55 degree infill smoother on everything that I've tried. It does not have the same cadillac feel in all wood (that's a weight issue), but for sure the surface is a bit better.
It's worth the trouble to learn to use the cap iron properly, even though it doesn't make us feel as warm and fuzzy as buying more planes (and if I'm not chief indian in the pack of plane buyers, I'm first assistant to the chief).
Maybe we can get a productive discussion going, and save a few people some bucks. It only takes a couple of weeks of use to learn to set the chipbreaker as tight as these videos without accidentally running it past the edge and over it (dinging up the edge in the process).