Hand Tools Archive
Surface is similar between both, quality slightly less uniform at 30 degrees but nothing that would bother someone who was going to scrape and sand or just sand. 35 degrees with 10 of clearance may result in slightly more bright surface. Larry always insisted that we were burnishing grain with common pitch planes. Maybe there is a little bit of truth to it.
As far as cutting force differing 30 to 35, I just can't perceive it with the cap iron set. Does the cap have anything to do with it? I don't know. Does the bronze sole of the LN plane have something to do with it (it's stick)? Not sure.
My takeaway from what I've done so far is that for the average person, 35 degrees will extend the time between sessions to the grinder and is probably a little easier for the average person to complete (unless the primary bevel is driven much shallower). 33 is the angle I manage to hit training myself to avoid edge quality issues. 35 freehand seems steep to me by hand, but the final bevel angle is a small tertiary bevel, not a full bevel. That may impact these results, or it may not. The length of the tertiary bevel is probably ...guessing....between a quarter and half micron at the most.
Secondary bevel in the charlesworth method, at least with my jigs, is 32 degrees.
I'm waffling about whether or not to use the guide to set an angle at 32 to see if it betters both of the others, but it really doesn't matter. It's unlikely to be anywhere close to the significance of the abrasive finish unless clearance is narrowed further.
The purpose off of the top of my head (getting lost in teh details a little bit) of measuring at 30 degrees was less about picking the perfect angle, but more about providing an alternate data point to keep people from reading the results and saying "pshawww...this test was done at 35 degrees. I know the results would be much different at 30"
I'm a later convert to these kinds of angles (30+), though, due to quality problems with A2, and knowing that I didn't observe them at 35º with the charlesworth method, and subsequent reading of Elliot's work confirming that he saw the same thing with alloy steels. Quality problems at that time outweighed any search for an extra 10 percent of planed wood, plus I realized that an undamaged iron without microchipping just made sharpening and subsequent quality easier to finish and attain, respectively. The microscope is telling me that perhaps I have sharpened 90% of the wear out sometimes, but not 100%. With an undamaged edge, you can hardly tell the difference between the two.
At any rate, I can assure you that the perceived force differences with the plane set up as I have it is very little, and that in both cases, the last 200 feet feel similar, while the gradual lowering of clearance before then also feels very similar. is my feel that accurate? i don't know. If not, ignorance is bliss.