I would suggest that what you are calling “common wisdom” is actually just current common practice or discussion. Over the years I have seen various techniques come and go about all things woodworking. The truth is there is no real “right” and “wrong” in woodworking, just different approaches to the craft and the truth is you can almost always get to the same end product using several different methods. What is “best” for one woodworker may not work at all for another because of differences in skill, tools, shop layout, or any number of factors. The idea is look at all of the available options and pick what works best for you and your situation.
You are partially correct on some of your statements. The ruler trick is used on plane blades by people who are in a rush (sharpening demonstrators) and don’t want to flatten the back as was traditionally done, or folks who see it as the best option to deal with issues such as pitting on old blades. Over time the back by mediaplayer” href=”#72033933″> bevel becomes a little larger and thus takes a longer each time to sharpen. There isn’t anything really wrong with using the ruler trick, in my opinion, but it can create some inconsistency unless you always use the same stones, rulers, etc. and you are having extra wear on the edges of the stone face which requires a little more maintenance of the stones. The slight change in cutting angle normally won’t effect use of the plane and could help prevent some tearout in figured hardwoods to a very small degree, with by mediaplayer” href=”#39176740″> bevel down planes anyway. I don’t believe back by mediaplayer” href=”#91413266″> beveling was done intentionally in “the-good-old-days” but I have found some evidence of back beveling in old blades. My belief is that some folks just got a little lazy during the sharpening process, or possibly just didn’t know and difference, and lifted the blade up when working on the back just to hasten working the edge. The bad news is that it is hard to go back to the flat back without grinding off the blade end. I really don’t think the “old-timers” were nearly as obsessed with tool processes or precision woodworking as is currently popular. They just knew of a process or technique that got them where they wanted to go and went with it. They knew when precision mattered and when it didn’t and used it by mediaplayer” href=”#38055152″> accordingly.
Chisels are kept flat so that you don’t have to lift them to get them to cut when used bevel up.
I am familiar with two types of chisel planes. One has the blade on the bottom and is used by mediaplayer” href=”#91385024″> bevel up. This one does function like a chisel and be back needs to be flat. The other type is essentially a low angle, by mediaplayer” href=”#69295927″> bevel up, pane configured so that the blade is foremost in the tool. You could the ruler trick on that blade with no negative results to the work.