When sharpening a knife, what exactly does honing do?
In: Engineering
Sharpening stone removes metal.
Honing rod pushes metal into place.
After the abrasive removes metal to create the shape, the edge is rough.
The honing rod pushes those tiny rough textures flat.
This flatness or polished edge does two things. It allows the blade to move through the object getting cut with less resistance.
But at the very edge of the blade, it makes that edge straight instead of jagged from abrasive that has scratched away metal.
Honing, stropping, ultimately all the steps are about trying to achieve a suitably keen and durable edge.
Part of this depends on the metal the blade is made from, part of it from the macro profile of the blade, and part from the edge geometry – the micro-convexing going on within around 1 micron of the edge.
Some excellent SEM images of what honing does can be found at https://scienceofsharp.com/home/ if you want to take a look.
You generally hone a blade with a set of stones of decreasing roughness, until you have achieved a suitable profile, and then strop until you’ve achieved the right microconvexity. A great deal of trial and error is involved, and a great deal of “feel” of the end result.
My own approach is to use a handful of stones to set the edge, then progress to a loaded leather strop with quarter micron diamonds, then a clean leather strop.
For a kitchen knife this is probably overkill, but for a straight razor its barely sufficient.
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