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A very quick and close look at 'steeling'

Discussion in 'Maintenance, Tinkering & Embellishment' started by HeavyHanded, May 18, 2012.

  1. HeavyHanded


    Jun 4, 2010
    The recent discussion re steeling with Stitchawl spurred me to take another look at this practice. Until now my experience with this activity has been largely limited to kitchen knives using a groved steel and a "smooth" one that had become discolored and somewhat abrasive. I've gotten poor performance when using the smooth one on the harder steels found in most pocket/hunting cutlery, even though I still use them on my softer kitchen knives with good results. Having taken a close look at many fresh and worn knife edges, I have never been comfortable with the "re-alignment" theory that is most often applied to the practice, so what is happening?

    I realize Verhoeven among many others have covered this topic already, but I have not. Here goes. Based on the micrographs and cutting tests I have a couple of observations. My test knife is a EKA H8 in 12C27 Sandvik. It was sharpened up to the fine side of a Norton Crystalon stone and deburred with the oil and swarf from the stone applied to newspaper (the best wayI know of to do a thorough deburring and not affect the grind structure). Test knife could shave arm hair and just dry shave facial stubble, though not clean to the skin. Could easily crosscut newspaper with a push cut, though sounded quite abrasive when doing so.

    The steel is smooth, though not mirror smooth. I cleaned it up thoroughly and polished it with white compound - very shiny and feels very slick when steeling. Pressure was very light, just enough to maintain contact.

    Pictures are at 160x and 640x

    First two are fresh off the stone and paper:



    Next two are after 5 passes on the smooth steel, increasing the angle only a degree or two. The edge exhibited a modest but obvious improvement on the stated tests relative to the starting edge - most notably the pitch of the sound it made going through newspaper became higher and more uniform.



    Last two are after 45 passes, some of the conventional wisdom suggests this could harm the edge. Testing showed a large improvement in cutting characteristics - dry facial stubble flew off my cheek without irritation and I was able to rapidly slice 1/4" strips from the crossgrain newspaper. Still no real evidence of burr or wire edge creation, though there appears to be something sporadic - visible lower right in the 160x pic that makes me think they're starting up in some spots...



    It is my opinion based on this test that steeling is in fact a form of sharpening (I have come to think of it as the opposite of stropping but achieving a similar outcome, and it quite possibly is realigning the edge, but I have to think this effect is minor compared to the "smoothing" effect I'm observing) using plastic flow instead of grinding to accomplish its goal. I can come up with no other explanation for what I'm seeing. The steel is not removed, but smeared/pressed/squashed, something that Verhoeven among others has already observed to some extent - unlike Verhoeven I observed no breakout of the apex and even after 45 passes I do not see any apex deformity that cannot be traced back the original grinding - this was a surprising find. I do suspect I could have stopped at 10-15 passes and perhaps gotten the best result I was going to get, but wanted to see the effect of too many passes. Clearly too much pressure would be devastating, esp combined with too many passes.

    Done carefully it appears capable of significantly improving a lightly worn edge or coarsely sharpened one. I'll have to do some more work on this using a more refined edge and see what the effect is. It may be (and makes perfect sense) that the more refined the edge the more important it becomes to use a glass steel, or one with very exacting surface treatment (has anyone tried chrome?)

    This is fast and effective - I'll be giving it a try on some of my larger knives next.
    Last edited: May 18, 2012
  2. thebrain


    Dec 12, 2007
    Great pics and info thank you. Once I was at a outdoor sporting show and there was an older gentleman who was sharpening knives as a way to sell sharpeners and steels ,he did a great job on my friends knife(I always have to sharpen it so it was a nice break for me) .The older man had some crazy smooth steels (mirror like smooth)for sale and some quite long ones(over 24inches) as well ,the steels he had for sale had a steep price.
  3. bluntcut

    bluntcut KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2012
    It would be useful to see the steeling-rod at 640x.

    Hands waving discussion.... Assumed parameters: i) hrc rod > blade ~ 62 vs 60, ii) rod is simple carbon steel, iii) rod is cylindrical. The rod steel grain boundaries angle can be combination of small/large/cross, essential the exposured grain & molecular lattice act as a cutter, abrading softer blade steel matrix = edge-leading stroke hone.
  4. David Martin

    David Martin

    Apr 7, 2008
    Thanks HH, for this information into a look at steeling and what it does to an edge. So, just a few light strokes, not the numerous pounding I observe most meat cutters doing. This helps to maintain the edge not hurting it as some put forth. DM
  5. Spinerazor


    Mar 30, 2012
    i use a steel on all my knives then strop to finish them up, i find it really aligns the edge well.
  6. Bigfattyt

    Bigfattyt Gold Member Gold Member

    Jun 23, 2007
    Yes, I have used chrome as a "steel"

    I have a hard smooth screw driver that I use occasionally when I roll an edge.

    True Butcher's steel will be smooth, with no micro serrations, or abrasives. The ones they sell in stores as steels these days actually remove quite a bit of steel.

    You can still order smooth butchers steels from shops on line.

    I always use a strop to finish up the edge.
    Last edited: May 19, 2012
  7. Chris "Anagarika"

    Chris "Anagarika"

    Mar 7, 2001
    Thanks for the insight. I'd try finding some smooth cylindrical object .. Not an easy task ;)
  8. Lagrangian


    Jun 25, 2011
    Hi HeavyHanded,

    Wonderful pictures and good commentary!

    In addition to Verhoeven, I think John Juranitch also looked at steeling (he wrote the book _Razor Edge Book Of Sharpening_ (2000)).

    Juranitch noted that using a smooth-steel would smooth the edge, and he showed some electron microscope pictures in a Popular Science article in 1997. I don't know how to access the full article, but excerpts of it and some of the images are available here:
    "The steeled edge has been smoothed out (top) into an even sharper cutting edge, as though someone had wiped the frosting on a cake with the side of a knife. Notice that there are no primary furrows (caused by the hone) left in the steeled area. Bottom photo shows a more heavily steeled edge. The metal has actually flowed back as though it were molten. This is an edge no hone will ever equal. But be careful not to over steel. In some microphotographs we've taken, you can see a thin hair of metal peeling away from such an over steeled edge. That ruins the edge and the blade has to be honed again. "
    --John Juranitch

    Some speculation on my part:
    (1) As you mention, it is not necessary to remove metal to smooth it out, since it could deform under plastic flow. I think this is called "burnishing" and has been used by Japanese sword makers. This is probably not for sharpening, but for part of their polishing/finishing of a sword. I haven't read it, but a friend of mine says that in this book on Japanese sword-making, an entire chapter (or half of a chapter) is devoted to polishing and burnishing.

    (2) I don't know if there is a formal definition for each of these and their differences, but it's worth thinking about:

    (a) Cutting/Milling (such as with a mill, cutting bit, or drill)
    (b) Grinding (such as with a sharpening stone)
    (c) Lapping (Workpiece is lapped against a softer medium with loose grit. I believe stropping is an example of this. The softer object is called a lap. Outside of knife-sharpening, the lap is often a softer metal, like copper or cast iron. The lap is softer than the workpiece, and abrasives will tend to embed in the lap. https://en.wikipedia.org/wiki/Lapping)
    (d) Polishing
    (e) Burnishing (Where the surface is smoothed by rubbing, but without abrasive removal of metal. https://en.wikipedia.org/wiki/Burnishing_(metal))

    One of the things I keep wondering about is work-hardening of metals, and whether or not that is happening to the knife edge during sharpening. In particular, I wonder if using a smooth steel causes any work-hardening of the edge in addition to possibly burnishing it. And, if work-hardening is happening at the knife edge, is this good or bad?

    For now, I have no answers, just questions and speculation.

    Thanks for your post! :)

    Last edited: May 19, 2012
  9. HeavyHanded


    Jun 4, 2010
    I have few ? that will be difficult to answer, but have a few assumptions I'll be working from.

    "Does this form of plastic flow weaken the edge?" followed by "does stropping on plain leather or newspaper use the same principle - plastic flow with no metal removal?" I do see some metal residue on my newspaper, but then I don't wash the blade off between grinding, stropping with oil/swarf, refining with slurry (all depending on what I'm doing) and the final newspaper polish. I don't ever see discoloration on paper when touching up a knife I've been using for a while.

    Second question - "If it does weaken the edge, wouldn't this effect be limited to the region of the apex - when viewed as a cross section - that falls outside the area left undisturbed by the grinding abrasive?" If so, one could safely 'steel' a large percentage of the edge irregularities without weakening the cutting line.
  10. HeavyHanded


    Jun 4, 2010

    I'll work on that - with an optical microscope at 640x the steel would look like a single line surrounded by blur. I'll give it a go and see if they're worth sharing - have to wait till Monday.

    The steel used for this thread is higher RC than the blade (probably, based on how much effort it took to polish it) and cylindrical. I assume using a flat steel would work too, but more pressure or # of passes might be needed? I did a test with a smooth stainless roller at work that yielded similar results - hardened somewhat, but I was able to cut the journals off with a hacksaw so either differentially heat treated or relatively low RC.

    I've also considered that it might be just a fine file (this is the belief I've always operated under re 'steeling'), but then why is the affected metal still attached, and why no burr when one sees how much metal is being moved in such a short period of time? To me this implies there's no grinding happening at any level.
    I've come across discussions on straight razor forums where the properties of "draw" and stropping speed were the topic. There was speculation that less draw meant higher stropping speed, more draw meant slower stropping speed - friction being the common element with the silica content merely increasing the friction coefficient and not really removing metal...anyone strop at 1-2 cm/second and still get good results stropping on plain leather?

    Now I'm hijacking my own thread :D

    EDIT: Not sure if I should even include this observation due to a lack of controls or repetition, but I've tested three steels - one smooth hard, one stainless hardened industrial roller, and one softer steel that I ground down from a grooved one. The hardened ones seem to do a better job and the softer one shows small scratches from only 100 or so passes with several knives, the harder ones show no scratches whatsoever with a roughly equal #. Just a thought...
    Last edited: May 19, 2012
  11. Lagrangian


    Jun 25, 2011
    Hi HeavyHanded,

    I speculate that it is possible that steeling and sharpening causes work-hardening of the edge. This is the common effect that some plumbers know: If you bend a copper tube once, it is very soft and will shape easily. Try to bend a copper tube many times, and it will stiffen, and then eventually break.

    _If_ work hardening is happening then we are likely to see the following effects:
    (1) The work hardened edge will be harder than the bulk steel of the knife.
    (2) Work hardened area of metal is likely to be more brittle.

    I think that as a grain of abrasive ploughes/cuts through a groove of the metal surface, it is probably causing work-hardening. But so much stuff is going on at the surface, I don't know if this is a reasonable possibility. I wish a metallurgist (such as Roman Landes) could come by and comment.

    I also speculate that many grains which move over the surface of the knife edge cause burnishing. I my (wild) speculation is that during stropping, burnishing happens more often than when grinding. However, I have no idea if this is significant at all, in practice (ie: grinding/lapping may be dominated by abrasive cutting rather than burnishing?).


    One thing we should be rather careful about is the difference between technical jargon and colloquial usage. For example, technically, when a metal gets work-hardened, it gets harder and stronger. By stronger, I mean things like tensile strength, or compressive strength (I think this is also called yield strength). However, colloquially, we say work-hardened metals are often weaker because they are more brittle (like bending metal back and forth to break it). Technically, we say the un-work-hardened metal is tougher, and colloquially we say it is less brittle. (I think there may be a technical measurement/definition of brittleness, but I don't know it.)

    I figure some of you know the difference between strength and toughness, but for those who do not, here is a super-quick tutorial:

    Strength is measured as a force per area that if you applied, would cause the material to fail (psi, Pascals). Generally, engineers consider two types of strength: compressive strength and tensile-strength. Compressive strength is how much pressure you would need to apply to bend or break the material, and tensile strength is how much stretching force (tension) you would need to apply per area to break it.

    Toughness is measured as how much energy is adsorbed by a sample that breaks. Sometimes toughness is measured as energy per area, but more typical is energy per volume. I have a conceptual understanding of toughness, but my technical understanding of it is not very good. I have heard that toughness is rather complicated. Although there is the Charpy test, it seems that not all toughness tests are the same. The shape of the sample is standardized in Charpy (I think?). But if you were to change the size or shape of the sample, you would get a different amount of energy per volume required to break the material. So which number is "the true toughness" ? I think both are, it's just that toughness varies depending on circumstances (such as geometry of the sample).

    Since force and energy are different, strength and toughness are different.

    If there are any real engineers or metallurgists out there, it would be great if you could chime in and comment or correct us.


    btw, early engineers of super-high-strength steels were confused about the difference between strength and toughness. The super-high strength steels were very very strong, but they were very very not-tough. In other words, they were brittle. This difference caused a lot of unexpected failures where a "stronger" steel would fail, and fail more dramatically than a weaker one. For example, the weaker steel might not fail at all, might get bent slightly, or might flex. But the stronger one would snap or shatter. The strong steel was stronger in that it required much more force than the weaker steel to fail (bend or break). It was only after such failures that engineers began to appreciate ductility in metals, and how ductile metals tend to be much tougher.

    Plastic flow takes energy, and if a material can undergo plastic flow relatively easily (ie: a ductile or malleable material), then a crack propagating through the material first causes plastic-deformation before continuing to grow. The "plastic zone" or "ductile flow" near the tip of the crack means it takes additional energy to grow the crack. For example, it is very hard to propagate a crack in a soft metal such as copper (unless of course, the copper has been work hardened). You would basically have to spend a ton of energy to "rip" a soft copper sheet. But it is trivial to propagate a crack in glass, which has almost zero ductility/malleability, and so a crack can grow while using almost no energy at all.

    You can read more about strength versus toughness in this wonderful popular-science book:
    _Why Things Break_ by Mark Eberhart (2003)
    If you are feeling a bit more ambitious, then a more involved book is by J.E. Gordon. More involved, and a little dated, but also at the popular-science level (although he does use some high school math):
    _The New Science of Strong Materials_ by J. E. Gordon (2006)

    In any case, I think we should just keep in mind when we are using colloquial terminology versus technical jargon. If this were a technical forum, I would suggest using the engineer's technical jargon, but I think that might not be the right choice in bladeforums.com where the community is extremely diverse?


    I'm a little concerned about being able to see grain boundaries in a microscope. They are there, and we should be able to see them, but it seems metallographers use chemical etchants make them more visible. As you know, they basically first polish a sample to a mirror finish (optically smooth) so that any features of the surface are not scratches from grinding (otherwise scratches might be mistaken for features in the bulk metal). They then etch this surface with chemicals that preferentially attack the grain boundaries (or preferentially attack the grain cells?). Here is a list of some etchants:

    I am unsure how much grain-boundary or carbides you will see without the chemical etchant. The user Clip on the Spyderdo forums appears to be working in a metallography lab, and he might have more information on this.

    That said, I think it is worth trying to look for them, even if you don't have any chemical etchants. If you find them, that would be super interesting! And would encourage others (like myself) to try to find them as well.



    P.S. There must be textbooks on metallography. I feel like I should go read a book on that, as well as one on metallurgy. My overall feeling is that we are starting to ask engineering questions, so we should go find out what engineers know. This will inform us, but not be the ultimate test: Whether or not we notice a difference in practice.
    Last edited: May 19, 2012
  12. tiguy7

    tiguy7 Gold Member Gold Member

    Jun 25, 2008
    If you're looking for a way to steel some of the harder alloys, use the sides of a ceramic blade. Most are very smooth and very hard.
  13. I've been wondering about this too. I've commented before, about how my habits are built around using smaller hones and strop blocks (usually less that 6" length). The short length of my strop block means I can't really take long, fast, sweeping passes on it with a blade. This means I'm stropping at a slower pace than might be ideal, which places a premium on making sure my edge is refined enough prior to stropping, so I can still accomplish what's needed on my edge with the strop.

    I've recently started using the inside (rough) face of my leather belt as a strop. I even applied some green compound to a ~12" section of it. With the longer stropping length, I'm taking what feels like a more 'natural' pass at it, faster paced and through a greater length. I'm getting great results this way, especially with carbon steel blades, like 1095. This has made me think more about the effect of velocity of the stroke on a strop. It's no secret, that even 'softer' materials can do some damage (i.e., abrasion) to much harder materials, if the two collide or interact at higher speed, where the effective mass of the 'softer' material is greatly multiplied (by the speed), and has a much greater effect than the actual hardness of the material.
  14. David Martin

    David Martin

    Apr 7, 2008
    Lagran, Good. Yes, I've noticed at times we forumites tend to misuse steel terms and thus introduces confusion into the discussion but members are at many different levels and experience so, this will happen.
    Big, The smooth steels only. Yes. There is a forum member that steels using a ceramic tubular electric insulator and claims great results. Some here may know the item I'm refering to. It being ceramic would be much harder and smoother than steel. Hence, better results could be obtained. Coming from a meat cutting background I always knew 'Something' was happening during steel but was unsure what, until now. Also, many meat cutters do it wrong. Many thanks to HH for taking this topic to the next level. Call it plastic flow or realigning, its easier for me to see this happening to a knife's apex when rubbed against a hard object than when a knife's edge is scrapped against something soft like leather. I think, how does that do this? Remember it's very thin metal that we're moving... Just my thoughts. DM
  15. Lagrangian


    Jun 25, 2011
    Sadly, the physics of friction is not well understood. So I'm not sure if there will be a good correlation between just friction and the effect on the edge.

    For example:

    A softer material can deform more easily, and therefore might make contact over a larger surface area (such as partially penetrating into grooves and crevicies). This in theory could increase friction. Also the deformation of the softer material (if it's plastic or rubbery, like leather) could increase the perceived friction because you spend energy deforming the surface as you draw the knife across it.

    But a harder (and rough material) may plow into the metal more, and so could have high friction due to extra cutting.

    So if there is higher friction, it may not be clear which effect(s) are happening.

    In addition, chemistry is also relevant to friction. I remember a chemist saying she thought Teflon was so slippery because it has very electro-negative molecule. Surface physics is almost ridiculously complicated... Which is good because there a huge variety of useful things that can happen. But it's bad in that it's so difficult to understand.

    The engineering study of materials which are in sliding contact, is also known as tribology.

  16. bluntcut

    bluntcut KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2012
    (1) The contact area between a rod (cylindrical) against a bevel is a line or point for V and convex bevel respectively. The force vector of impact is downward+large and without abrasive, (Lagrangian's 1) most likely steel burnishing/plastic-flow is the end result. For grove-rod the indentation is deeper into the blade, which change the force-vector to lateral, with enough pressure/force it will break the metallic bond especially at the cutting edge - serration as intended - I guess. Grain boundaries (gap between angle) too shallow to change vector direction.

    (2) I am not a chemist... Edge work-hardening (gain strength, loss toughness) require thermal<=>kinetic energy to bring the steel lattice to a lower engergy potential (stronger steel lattice convalent bond structure== +strength, in turn weaken inter-steel-lattice metallic bond== -toughness). I don't think steeling impart enough energy to work-harden most blade steel.

    Hone using rod - lead+trail strokes, will it yields smoother bevel surface? Should end with edge leading strokes to push metal away from the cutting edge.
  17. Lagrangian


    Jun 25, 2011
    Hi bluntcut,

    I think I agree with most of your points in (1). I'm less sure about the grooved-rod discussion, beacuse I simply don't know. I imagine a grooved rod has a lot of cylindrical bumps on it? I guess I'm a little confused. What do you mean by "latteral" ? Is that just perpendicular to the surface normal?

    As for (2), I don't think what you're saying is right. For example, just bending metal will work-harden it. The reason is that work-hardening is caused by mechanical deformation of metal grains; it basically destroys the regular crystal structure of the grains by sheering which introduces dislocations (defects) into the crystal structure. Generally, when you force a metal to undergo plastic-flow, it work-hardens.

    If you were to bend or crease aluminum foil, or copper foil, it would still work-harden. Household alumium foil is about 16 microns thick. The very edge of a knife is very thin (around 0.4 microns according to Prof. Verhoeven), and is quite easy to bend. In fact, when sharpeners talk about "flopping the burr back and forth by sharpening alternate sides until it breaks off" they may be talking, in part, about work-hardening. Just like bending a thin bar of copper (or steel) back and forth until it breaks. That bending is a form of plastic flow, which in turn is likely to cause work-hardening. At least that's my speculation about the burr (I'm not a metallurgist).

    "Work hardening, also known as strain hardening or cold working, is the strengthening of a metal by plastic deformation. This strengthening occurs because of dislocation movements within the crystal structure of the material."--wikipedia

    The very edge of a knife is kind of counter-inuitive, in that it's a very tiny volume, and a very tiny surface. So even a little energy into an even tinier volume/area is a pretty high energy density! It can be enough to transform the metal, but just over a tiny area/volume.

    Last edited: May 19, 2012
  18. bluntcut

    bluntcut KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2012
    After some thoughts - to reduce physics, let's envision a snow plower outfit with a vertical steel sheet (groove) or steel drum (rod). Plow 10cm of snow using steel sheet would remove most snow, while using a steel drum would pact the snow. The weight of the plower is force perpendicular to surface, moving forward is lateral (maybe just for lack of better term) force parrallel to surface, due to steel drum curvature this force deflect downward + riding on top of snow ensure more downward. on other hand, steel sheet would mostly scrape the snow away.

    According to the definition of work-hardening - you're right. :saturn:I was thinking more in line of tempering where steel lattice configuration changes rather than inter-lattice or grain level deformation. For example: cpm-m4 become harder with temperature going up (to certain point before softening occurs).
  19. stoffi


    Jan 14, 2008

    I interpret your images not as if the steel has been squashed out, but rather, that the metal has been polished in another direction than the sharpening lines (perpendicular) and with a fine medium (the steel). I don't believe you could actually squash the metal as you're suggesting, since the steel is too hard to deform with such little force and especially since it is supported by the surrounding steel. It's sort of like insisting on squashing out the back of a metal pan by caressing it with another one. However, a burr or rolled edge will definitely align back into place, because there is less supported metal to "grab hold of", or shove around; just as it is easy to bend soft sheet metal around -- but it would be harder to squash it out. You'd need to hammer it hard.
    Last edited: May 19, 2012
  20. stitchawl


    Jul 26, 2008
    Brilliant work and wonderful comments by all of you folks! Great information here!
    Thanks for taking the time and making the effort to help us all understand the processes involved.
    And for the folks reading this thread who don't quite follow the science behind it all, keep in mind that you don't have to have a doctorate in Electrical Engineering to turn on the living room lights. All you need to do is flip the switch.


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