It is pretty common to see references to the "paper test" for checking for sharpness of an edge -- the idea that you should be able to lightly rest the blade against the edge of a piece of paper and it should "bite" by itself and easily slice through the sheet with hardly any pressure. For example, out of the box a disposable safety razor blade will easily pass this test.
Now, I'm a beginner at woodworking and I've been trying to learn to sharpen tools -- I bought some inexpensive Dewalt chisels a long time ago and more recently a Mora whittling knife to practice sharpening with. (I've got a Stanley No 4 plane arriving soon from eBay, as well.) After a decent amount of practice (using DMT interrupted diamond stones up to Extra Fine or 3M microfinishing film on plate glass to 15u, stropped on chromium oxide on leather in both cases afterward), I'm able to get them to pass a lot of other common sharpness tests:
- Shaving hair cleanly (everything from coarse leg hair to very fine knuckle hair)
- Edge catches on the surface of your thumbnail without sliding
- No light reflects off the edge itself, no visible burr, no chips or nicks under a loupe
- Visibly reflective/polished looking bevel surfaces near the edge
- Edge feeling very sharp to touch with the pad of the thumb, and I cannot feel a burr on either side
- Edge feeling extremely smooth (like glass) when drawing the tip of your fingernail along the blade
- And most importantly, when cutting wood they leave a nice smooth surface, especially when cutting with the grain.
Despite that, one thing I can never seem to do reliably is make them pass the "paper test." Usually I get intermittent results -- sometimes the paper buckles, sometimes it cuts "alright", but most often it cuts a short ways but then stops or jams. It's definitely not as impressive as I've seen proper razor blades do.
Normally I would just say the only thing that matters is how they cut wood -- but as a beginner I don't really know whether I'm experiencing more resistance than I should, or what the shavings should really look like when you try to shave end grain, and so on. In the absence of using "properly sharp" tools myself I really don't have a feel for what I should expect from a tactile perspective or an "end result" perspective.
So, my questions are:
- Should I actually expect to be able to sharpen decent quality bench chisels, plane blades, whittling knives, etc. to the point they can pass the "paper test" when using the normal bevel angles? Or is this futile just because of the bevel angles and thicknesses of the tools involved, compared to razors which are comparatively thinner and with more acute bevel angles? For a while I was sure the dewalt chisels just had crappy steel or poor heat treatment, but, honestly, the Mora which should have decent steel/treatment has similar problems.
- Even if I could, is it a useful indicator for the tasks hand planes, bench chisels, whittling knives, etc perform? Am I missing out on a "final level of sharpness" or is an effortless paper-cutting edge on these tools just going to be demolished after cutting through a few inches of actual wood, even with good blade material?
It would be tremendously helpful to know whether I'm getting myself frustrated over something that is either impossible or unimportant.
UPDATE: After actually actually POLISHING the bevel of this chisel on the chromium oxide-on-leather -- say like 50x eight inch long passes on the bevel and 5-10x on the flat (instead of just a very light stropping), the results have improved dramatically. I'm able to take very thin shavings off of end grain and it looks pretty smooth. Fresh off honing it will pop some leg hair although it's not 100% -- I'm wondering if my arm hair is just too fine? -- and it also does significantly better on the paper test, although not perfectly.
Here's what it does to eastern white pine endgrain: