# Why does sawing action increase the effectiveness of cutting knives?

From practical experience, it's obvious that a sharp non-serrated knife will cut items with more ease if the user attempts a sawing motion.

The intuitive reasoning for how a non-serrated knife cuts - the blade is sharpened to just several atoms thick on the edge and whatever is being cut simply can't hold up to forces applied across such a small area - obviously breaks down here. (Experimentation!)

The most logical explanation that occurs to me is that the knife is imperfectly sharpened, leading to micro-serrations that assist cutting. To utilize these imperfections, one must use a sawing action while slicing.

Can anyone explain what's going on here?

• I don't think knives are sharpened to a few atoms thick, but the sawing likely depends on the material. Nobody saws butter for example. Stringy fibers in meat (appetizing, right?), cut better when stretched (by the back and forth) while being cut similar to how a taut string cuts more easily than a lose one by a scissor. Sawing is also a more natural human motion. Ease of movement should be taken into account too. Nov 20, 2017 at 5:46
• Possibly relevant question: physics.stackexchange.com/q/134119/26969 Nov 20, 2017 at 5:47
• I'll add that nobody saws the skin off an apple, just straight pressure with a flat blade while steak is usually cut with serrated blade. The difference is the structure of the material being cut. Nov 20, 2017 at 5:51
• @userLTK It was something I'd heard. Some definitely are sharpened that much, though maybe not a common kitchen knife. Also, I'm not referring to actual "sawing"; it's just the term that best describes it. What else do you call it when you wiggle the knife in the plane of the blade a bit? Nov 20, 2017 at 6:02
• Your logic is correct. There are two sharpening techniques, German using a sharpening steel that makes micro-serrations requiring a sawing action to engage, and Japanese using super fine sharpener stones (up to 8000 grit) to make the blade razor sharp that does not require a sawing action. Nov 20, 2017 at 7:24