My Theory on Overhoning Straight Razors – Part 2

This is the second installment of My Theory on Overhoning Straight Razors. Part 1 Can be found here.

The next problem with the theory of overhoning is a little more complicated. That is the part that says that an edge is and/or can be  “too refined”.

The way I see it, any given stone will only “allow” an edge to be as thin or as thick as the height and depth that the abrasives can cut. For example, an 8K edge will only ever be as thin as the depth of the scratches made by the 8K abrasive. If it is too thin, then the 8K abrasive will cut through the steel. 16K should theoretically allow for the edge to be half as wide as the 8K, and so on. In this view, overhoning is technically  impossible because the edge is continually renewed at a constant thickness.

When honing razors, the overall agreed upon minimum refinement for a razor is 8K or abrasives as small as about 2 microns. It is 8K because this is the level at which the edge of the edge becomes thin enough to comfortably sever the hairs on your face 6-7 days a week, but thick enough to hold up to 5-6 shaves in between touch ups.

This has led to a rise in the belief that if the edge becomes too refined, it  will be too weak to hold up to a shave, or it’s lifespan will be greatly reduced. The more recent upper limit was .25 micron in refinement, or about 60K. This idea has been challenged since the first .125 Micron CBN (that’s 120K) edges started coming out. (Here’s a review of one of the first documented .125 micron CBN edges from 12/2010) We have since moved on to .1 micron (150K) and even into 50 and 25 nanometer edges (.050 and .025 microns or 300K and 600K, respectively!).

It is without a doubt that more refinement does yield a closer shave (whether or not it is smoother and/or sharper is another topic entirely 🙂 ).  But there is a tradeoff that must be acknowledged as refinement increases – the edge of the edge becomes thinner as it becomes more refined, thus inherently more fragile. (It certainly cuts through hair much better, though!) So can be seen as true that an edge with more refinement will not hold up as long as one with less refinement. However, it can also be said that a closer shave lasts longer than one that’s not as close. But in terms of overhoning, the abrasive’s characteristics determine the thickness of the edge. The rest is reliant upon the steel quality and geometry. Good technique doesn’t hurt, either!

Bart Torfs, who is probably the the world’s leading authority on Coticules, summed up on a B&B thread what I am thinking much better than I can:

This pretty much concurs with what I always assumed to be going on with small chips that can be seen under magnification immediately after honing. They are just the deepest remnants of a saw tooth pattern left by the coarser stages of bevel formation.
“Overhoning” by the definition of an edge disintegrating once it is supposedly taken beyond the keenness limit of a particular hone, is a hoax.
If the blade in the picture is honed further on the stone it was finished with, there will be no new chips to form. Quite the contrary: more metal will be removed and the boundry that forms the very edge will slowly shift towards the bottom of the chips. The finishing hone may be too slow to “hone the chips out” within a reasonable time frame, but that is what eventually would happen.
There is no single physical reason why a hone could abrade “through” the bevel. In fact, the hone only “abraded through” the steel at the very apex of the bevel. It leaves a particular type of edge jaggedness akin to that particular type of hone. The only reason why there could ever fall fragments out of the bevel, that are larger than a hone’s normal abrasion, is when there is structural damage in the steel, caused by corrosion or stresses induced by erroneous tempering.

So in the end, one must choose for themselves – just be sure not to overhone your edge! 😀

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3 Responses to “My Theory on Overhoning Straight Razors – Part 2”

  1. Wicked Edge Micro Fine ceramic stones: first impressions | Molecule Polishing Says:

    […] only get revealed by the 0.6 micron stones. This is the “overhoning is a hoax” effect Tom has written about.) Edge after sharpening with 0.6 micron ceramic […]

  2. Antonio Ceci Says:

    I LOVE reading your articles. They are extremely detailed and professional. I agree with every word you wrote. Well done! 🙂

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