My Theory on Overhoning Straight Razors – Part 1

We had knife sharpening competition with some heavy hitters in the Keeping Sharp sub-forum of the Knife Forums. The idea behind this one started out for guided devices such as the Wicked Edge (WEPS) and the Edge Pro, but quickly turned into a friendly “Clash of the Titans” with several methods of sharpening represented –  from freehand to Edge Pro to  WEPS to belt sanders. The thread can be found here.

As the host and honorary judge of this competition, I supplied 7″ Maestro Wu Bombshell Steel Chef Knives to the participants, without knowing who got which knife. I knew there would be no clear winner, and my main goal was to make this a learning project. And learn I did. The knives were all amazingly sharp and well done.

I took microscope pictures of before and after the cutting tests – and it is from these pictures that this blog post is based to support my theories on Overhoning straight razors. I know these aren’t straight razors, but the similarities to what I saw on straights when I honed and on what I saw on these knives sharpened by others gave some quantitative support to my long lingering theories. Besides, the guys sharpening were no hacks, and approached their sharpening in a similar fashion to straight razor honers.

All pictures here were taken with a Veho 200x USB microscope. Original resolution size is 1mm high x 2.5mm wide.

OVERHONING

Overhoning is a controversial topic amongst straight razor honers. Most people who know me know that I respectfully do not subscribe to the theory, which basically states that too many strokes on a hone will cause the edge to become a “foil edge”, which is too thin to support itself and folds over during the shave; and/or cause microchipping in the final, and most delicate stages of razor honing.

As far as foil edges on straight razors caused by overhoning, the thickness of the spine of the razor combined with the width of the blade determines the edge angle. Since we hone razors with the spine flat on the stones or strops, the geometry is predetermined. If the edge angle should be too low and the steel quality isn’t able to support such an angle, it will fold or break. This isn’t  a direct consequence of overhoning, as in too many strokes. It’s clearly one of geometry. Increasing the angle by adding a layer of tape will reinforce the geometry, thus stopping the breakdown or foiling when honing.

Once geometry is accounted for, one can arguably hone past the point of ideal or what is considered “enough” – in other words, “overhone” in the sense that you took more passes on the hone than was necessary. However, this shouldn’t raise a burr (with single side passes as in straight razor honing) but will continue to reinforce the geometry that is there. In an example taken from knife sharpening, where a burr is often formed and is the indicator for “sharp” on one side, it clearly is honed passed the point of “ideal”, but there is no foiling of the edge once the burr has been removed (unless the angle is too acute). The same applies to razors. Once you get “there” you will only continue to reinforce that angle. Of course, the idea is to know when to stop, but that is another issue (I’m not addressing the spine wear issue here)  :)

That brings us to the argument of  microchipping as a result of overhoning. It has long been my belief that what really happens is that each successive level of refinement ultimately exposes ever deeper scratches left behind from earlier stages as it establishes it’s own scratches. In fact, it’s not that the edge actually chips, it’s that the edge is refined enough with smaller scratches around it to reveal the gap left by the deeper scratch!

Below is a perfect example – the vertical deeper scratches lead directly to a microchip in the polished edge.

Microchip 1

Microchip 1 (200x)

However, microchipping at the finishing stages is a real phenominon, as anyone who has honed a razor has probably seen the semi-circular chip-out just left of center, below:

Common Straight Razor Microchip (200x)

This micro chip, and the triangular one to the right are often attributed to overhoning because these chips only appear at the final stages of honing. While I said before that the microchipping were preexisting gaps that become exposed, it could also be that because the scratches are so relatively deep, by the time  the razor is honed to such a thin and even plane at the edge, a preexisting deeper scratch causes the chipout due to lack of support from the steel around it – a weak link, if you will.

Let’s take a closer look at that microchip and how it most likely formed:

Microchipping closeup (200x enlarged and cropped)

If you follow the chip upwards from the edge, a deeper scratch is revealed in the bevel, as marked by the arrows. In other words, the deepest scratches from a coarser stone/belt/diamond plate had not yet been completely removed and only when the edge becomes thin enough so one can shave with it does the earlier damage become apparent.

At this point, an argument for the theory of underhoning  – not overhoning – can be made.

Something to think about :)

In Part 2 I will discuss my theories on overhoning in regards to edges that are deemed “too refined”.


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12 Responses to “My Theory on Overhoning Straight Razors – Part 1”

  1. Josh Says:

    Excellent observations Tom! I think you are right on about it actually being due to under-honing the edge instead of over-honing. Thanks for the great info!

  2. Josh Says:

    ha, thanks! that was done on my EP, but i’m waiting on a WEPS from Clay now! unfortunatly it will be several weeks =(.

    so, in your experience, will ultra-refining an edge with all diamond stones/sprays to .25u cause chipping? that is what i ordered from wicked edge… mainly cuz i want to be able to sharpen ceramics AND straights… your thoughts?

    oh, and that microscope you have is amazing! thanks for the photos again!

  3. Jende Industries Says:

    Great question about the diamonds, Josh! It’s a complicated answer that isn’t just a simple yes or no. Basically, if you do it right, you should have minimal chipping at all levels. But it’s more technique than abrasive medium, IMO.

    For ceramics, you will need Diamonds for sure, but since there is no burr – it is more about making controlled serrations.The technique is different than regular steel knives.

    Straights are yet another breed, and you shouldn’t need a guided system for them, in general – not that you can’t use them.

    If it’s OK, I will contact you from your website and we can discuss this all in greater detail :)

    The WEPS is simply wonderful, and worth the wait. Having both the EP and WEPS will give you some serious flexibility when choosing the optimal system for a specific sharpening need.

    It sounds like you need to join us on the knife forums!

  4. Luka Says:

    Hi! Can you please help me with the “simple” decision? I’ve decided to buy three whetstones (classic size, not EP or anything like that) and I was thinking about Shapton 120, Chosera 1000 and Chosera 5000. I have global chef’s knife g-2, cromova steel, 58 hrc I think. Also Tojiro Senkou paring knife (vg-10, 62 hrc) and few Dick knives that are in a bad shape. What do you think about my choice, would you go for all Shaptons are all Chosera? What about grit? Any suggestions? :) Thank you very very much cause I’m indeed curled up naked in the corner sucking my thumb, not laughing ;D

    • Jende Industries Says:

      Luka, I’m a die-hard Shapton fan, so of course I suggest Shaptons! :D However, Choseras are also excellent stones. Do you like Coke or Pepsi? You can’t really go wrong with either line. I’d first recommend Shapton Glass since you are dealing with some VG10 and RC 62. An excellent setup is the #320, 2K, 6K, or a #220, 1K, 4K. For Choseras, I recommend a #400, 1K, 5K. If you are a more confident sharpener, you can have some larger jumps between grits, but if you are less confident, then keeping a closer progression is better. I hope this helps, and thanks for reading!

  5. Re: Murray Carter’s Razor Sharpening Video (and the surrounding debate) « Jende Industries Blog Says:

    [...] (from top left to bottom right). So at this stage, you can also attribute the chipping to “underhoning” which describes chipping that is caused by revealing the deepest scratches left by the [...]

  6. Wicked Edge (WEPS) Stock Diamond & Ceramic Microscopic Progression « Jende Industries Blog Says:

    [...] out in order to prevent/minimize micro chipping at the finer stages (see my reasoning about that, here). WEPS 100 Diamond – [...]

  7. Wicked Edge (WEPS) Shapton Pro Stone Microscopic Progression « Jende Industries Blog Says:

    [...] be adjusted with geometry, but every edge will ultimately approach  the same 0 width dilemma (see this post for more about the theory of over [...]

  8. Honing a Straight Razor on a Coticule – Micrograph Progression | Jende Industries Blog Says:

    […] of cutting action with a light slurry, and as the edge of the edge shows, it is starting to expose microchipping from the heavier slurry that previously cut through it. The bevel itself, however, has less surface […]

  9. A theory on Over Honing (not mine BUT interesting) Says:

    […] Greetings! interesting read. I don't know if this is a common alternate theory; if it is well known, but I'd love to hear what Honemiesters or other think about it. It basically states that one can't over hone. That the geometry of the razor prevents this. That the phemenon of 'flaking' is really the 'uncovering' of scratches that occurred on lower grit stones. Here is the link: My Theory on Overhoning Straight Razors – Part 1 | Jende Industries Blog […]

  10. A theory on Over Honing (not mine BUT interesting) Says:

    […] Greetings! interesting read. I don't know if this is a common alternate theory; if it is well known, but I'd love to hear what Honemiesters or other think about it. It basically states that one can't over hone. That the geometry of the razor prevents this. That the phemenon of 'flaking' is really the 'uncovering' of scratches that occurred on lower grit stones. Oh, and for guys like me…there are some cool pictures… Here is the link: My Theory on Overhoning Straight Razors – Part 1 | Jende Industries Blog […]

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