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Thread: leading edge vs. trailing edge sharpening?

  1. #1
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    leading edge vs. trailing edge sharpening?


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    Most of the recommendations that I've seen in the past for sharpening with a stone involve leading edge sharpening. I witnessed someone at a knife show freehand sharpening a blade on a bench stone with circular motions, which is a mixture of leading edge and trailing edge. I've also seen videos of the Sharpmaker, maybe even official Spyderco videos, showing going both directions. And lastly I gather that people that use paper wheels are limited to trailing edge sharpening.

    I'm wondering if there are situations where leading edge sharpening can actually dull an edge. If a stone is soft, or not perfectly smooth or flat, or is loaded with particles, can that be a problem? I ask because when I use my sharpmaker it doesn't seem to go beyond a certain amount of sharpness. Some edges of my stones seem to be a little rough and I don't know if that is a problem or not.

    Trailing edge sharpening would be a little difficult with a Sharpmaker, but I've been using a DMT Aligner and it would work perfectly well with trailing edge action.

  2. #2
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    My opinion is that either way will work. I used leading edge sharpening for years on an old "whet rock". I now use trailing edge on my paper wheels, primarily because of safety reasons. I would think that leading edge sharpening could cause problems if the medium is not smooth. If you had a rough spot on your stone for instance, you could damage the edge easier by grinding into the imperfection, than if you were sliding your blade over the same bad spot. To me, sliding over is easier than running into a defect in the stone etc. Purely theoretical thinking in my less than alert mind!

    Blessings,

    Omar

  3. #3
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    Yes, most power tool methods will require trailing edge, as a wheel can catch/damage/flip your knife and you stand an excellent chance of cutting through an abrasive belt. Sharpening by hand or with a clamped system, both will work---hell, going back and forth like a bow on a violin works too, and actually helps maintain a very consistent bevel--I've sometimes used this method when I want to establish a back bevel and only have small sharpening surfaces to work on (pocket sized stones), though it requires a high polish so you don't have deep score lines parallel to the edge acting as stress risers, and I always capped it with a microbevel ground perpendicular to the edge. Anyway, back to the topic...

    It's been my experience that on some "gummier" low carbon steels--and especially those with lots of chromium like the lower 440 series (A and B) as well as AUS-6, 425M and a few of the other old boys, that trailing edge sharpening tended to produce more of a wire edge, where leading edge would often break the wire edge off or not let much of one form. Of course, if you have a scrap piece of hardwood available to pull your edge across, wire edges are not that big of a deal, but it's something I noticed. Now, on most tool steels, and the more modern stainless steels I've not noticed much of a difference at all. I've heard that on new diamond stones, especially very coarse ones, you should do trailing edge versus leading edge because the edge can rip out the more proud/prominent diamond pieces before they've dulled a tad, but I've never attempted to verify this.

    Either way, just work on maintaining a very consistent angle, and let the sharpener do the cutting versus trying to speed it up by pushing into it with a lot of force.

  4. #4
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    I approach sharpening with a few basic steps.

    1. De-stressing the edge: Remove damaged metal (chips, folded edge) etc from edge. This is by cutting with the edge into the stone
    2. Shaping the edge: Shaping until no light is reflected back from edge. This can be done either way, but lately I have been using circular motions for a while, then shift over to edge leading strokes.
    3. Apexing: Increase the angle, very lightly apply micro bevel to remove any burr
    4. Refinement: Edge leading.

    I changed to edge leading strokes after seeing the following a while back:

    Apex-Bevel-Geometry-cross-sectional/page2

    Quote Originally Posted by bluntcut View Post
    I spent considerable amount of time on the physics & visualization of sharpening grind interaction -> I gave up (more like deferred) for now, since who the heck want to read this dissertation anyway (ok, maybe a few of ya).

    Alright then, booted myself back to Keep-Simple principle.

    Sharpening stroke direction - edge trailing or edge leading or combination? I found a while back (re-invented the wheel - only sharpmaker is the purist) that edge leading stroke worked better than trailing/stropping stroke. Here is an easy experiment you can easily replicate.

    Setup


    Used DMT 6EF to de-burred: Used light pressure strop strokes for edge-trailing sample. Used light pressure edge-leading strokes for edge-leading sample.

    Results


    I don't have a SEM & SW (to construct field depth) to give a good edge/apex facing view. Just to show that 'Edge-leading 90* deburred' edge is clean and thinner than 'Edge-trailing'. I am not going to blah about variables this & that at play.

    Experiments on Knife Sharpening by
    John D. Verhoeven, Emeritus Professor, Department of Materials Science and Engineering
    Iowa State University, Ames, IA, September 2004

    Was also influential for me as I want to keep Burr formation to a minimum.

    "All of the sharpening done on the waterstones moved the blade along the stone in
    the direction into the blade edge causing the abrasive debris to move away from the edge.
    It was theorized that moving in this direction would reduce the bur size at the edge by
    preventing the debris from being deposited along the edge. To see if this theory was
    supported by evidence an experiment was done on the 6000 grit waterstone where the 10
    4-stroke cycles were all done with the blade edge moving away-from rather than into the
    stone surface. The results are shown in Fig. 27. Comparing Figs 25 and 27 one sees that
    moving the blade away-from the edge, as in Fig. 27, does seem to produce a significantly
    larger bur than moving it into the edge, as in Fig. 25. The larger bur is also accompanied
    by an increase in edge roughness, as shown in the face views."

  5. #5
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    Okay, this might sound like an odd question, but I'm pretty new to sharpen in general (only ever used a Sharpmaker and a leather strop), but do you have to change your sharpening angle as you go through the edge? For example, when moving from the the straight portion of the edge, to the belly and finally to the tip.

  6. #6
    Quote Originally Posted by JSMcustoms View Post
    Okay, this might sound like an odd question, but I'm pretty new to sharpen in general (only ever used a Sharpmaker and a leather strop), but do you have to change your sharpening angle as you go through the edge? For example, when moving from the the straight portion of the edge, to the belly and finally to the tip.
    Kind of off-topic unless I'm misunderstanding...

    But in the jist of it, think of the knife in three dimensional terms. You have your X, Y and Z axis. Your X travels from tip to pommel, and your Y from the bottom edge to spine. The angle of axis Y is what we consider the cutting edge angle, so whatever angle you hold this axis in relation to the stone is your edge angle. The X axis on the other hand, needs to be pitched up and down to maintain contact between the bevel and the abrasive surface. The challenge is in lifting and lowering the handle of the knife to manipulate your X axis angle, while maintaining the Y axis angle at a constant.

    Put more simply: Keep your edge angle the same, but lower the pommel of your knife up and down to match the contours.

  7. #7
    As an aside, circular motions freehand on a stone will yield a convex edge. The larger the circles, the more pronounced the convex, in my experience. Forward/backward scrubbing tends to produce a reasonably consistent edge angle, and is the way I reprofile on a bench stone. Higher grits up, I use exclusively edge-leading, for reasons demonstrated in the photographs in bluntcut's post.

    If a stone is soft, or not perfectly smooth or flat, or is loaded with particles, I would expect either leading- or trailing-edge sharpening to be less than ideal; for that reason I use manmade waterstones and flatten them regularly.

  8. #8
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    The truth of the matter is, while there are some minor technical differences, in the end either method will work just fine in putting an effective edge on a knife. This ain't rocket science. As long as you are removing steel and forming a bevel that meets about in the center, you will get an edge. I use both leding edge and circle method, depending on the size and what knife I'm sharpening. I use edge trailing while stropping on a cement step and have got good results. My sister in law Diane is the best sis in law a guy could have, but she's afraid of sharp knives. Won't have one in her kitchen. So when she mad a nice roast for dinner one night, and then asked me to slice it, I took one of her dull butcher knives out front, and stropped it on the top smooth cement step. Edge trailing. It got good and sharp and I pulled it through on the fence post to remove the wire edge. It sliced well cooked pork roast smooth as silk. Now she keeps it wrapped up in a towel for me to use when I am there.

    When I was stationed in Italy, I had an off base apartment rented. I'd get home when all the Italian ladies were starting to get dinner cooked for their families. First thing my land lady did was go out front to the old stone steps and strop her dark gray bladed old kitchen knife. They all did it. It must have worked because dinner in that part of Italy was usually some sort of meat dish, and it got sliced and diced.

    It's like standing front of the barn wondering which way to go. In the end, right or left, you'll still get around to the other side of the barn. As long as you have two bevels meeting in the middle, and you deburr the edge, it will be good.

    Carl.

  9. #9
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    Quote Originally Posted by bdmicarta View Post
    Most of the recommendations that I've seen in the past for sharpening with a stone involve leading edge sharpening. I witnessed someone at a knife show freehand sharpening a blade on a bench stone with circular motions, which is a mixture of leading edge and trailing edge. I've also seen videos of the Sharpmaker, maybe even official Spyderco videos, showing going both directions. And lastly I gather that people that use paper wheels are limited to trailing edge sharpening.

    I'm wondering if there are situations where leading edge sharpening can actually dull an edge. If a stone is soft, or not perfectly smooth or flat, or is loaded with particles, can that be a problem? I ask because when I use my sharpmaker it doesn't seem to go beyond a certain amount of sharpness. Some edges of my stones seem to be a little rough and I don't know if that is a problem or not.

    Trailing edge sharpening would be a little difficult with a Sharpmaker, but I've been using a DMT Aligner and it would work perfectly well with trailing edge action.
    In general (and there are always exceptions), edge lead on hard, fixed abrasives. Edge trail on loose abrasives. Situations where it isn't straightforward one must experiment. On some waterstones, a leading stroke will 'dull' the edge. On a hard stone, ceramic or otherwise, edge trailing will almost certainly leave a burr/wire edge. Sandpaper can be used either way, but will frequently produce a cleaner edge if used leading for at least a few passes to finish. Operating any abrasive at machine speeds changes a bunch of factors that make trailing edge cleaner than it might be at hand speed, all other things being equal.

  10. #10
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    I just replied along similar lines in another thread, regarding how I've learned to minimize burring/wire edges (either trailing or leading, but most of my sharpening is edge-trailing lately). I really do believe that the pressure exerted makes most of the difference with burrs & wires, and direction of stroke hasn't played as much into it, in my own habits. As mentioned, some stones with loose grit can be a problem with edge-leading. I've noticed it on soft Arkansas stones and other cheap stones that don't hold the grit very well, so trailing-edge sharpening seems to do better with those.

    Here is what I posted in the other thread:

    Based on the habits I originally formed when using a ceramic pocket hone in-hand, I've figured out that regulating pressure is easier if the hone (strop) is held almost vertical, or angled slightly off of vertical, and directing the sharpening/stropping stroke along that more vertical plane. Not so much weight (literally by gravity) is directly down into the hone/strop this way, as it would be if the hone were laying flat (horizontal) on a table or bench. For me, it is always more difficult to minimize or regulate pressure when standing over and leaning into the hone when it's laying on the table, and the edge is always going to take the brunt of it.

    I still prefer to go thinner and firmer for my stropping surfaces, so there's much less opportunity to round over the apex. Use the vertical or near-vertical angling of the hone/strop to regulate and/or minimize the pressure on the edge. Alternatively, you could also place the hone/strop on the table or bench as usual, but operate from a position that's lower, relative to the table, so your stroke is away & back in a plane that's nearly at eye-level, or slightly below eye-level. The whole idea is to minimize how much of your own weight and pressure is above the plane of the hone/strop. This may all sound a bit odd as compared to the 'proper' bench technique demonstrated by so many 'expert' sharpeners, but I've come to realize how much it's worked for me, in approaching it this way.

    David

  11. #11
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    Trailing edge sharpening would be a little difficult with a Sharpmaker, but I've been using a DMT Aligner and it would work perfectly well with trailing edge action.
    You can also place the Sharpmaker rods in the slots side by side under the base and use it as you would a bench stone with edge leading, edge trailing or circular strokes.
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  12. #12
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    David, I like that idea to minimize pressure! Alternatively bdmicarta, you can use a stropping surface with "no" give as demonstrated by HeavyHanded and Murray Carter in one of their videos using a sheet of paper on hard backing with surface structure for tactile feedback (+- compound). I have been using this method for touching up and maintaining sharpness on my scandi knife with great success (no risk of microbeveling or rounding the edge) and it can be used indefinetely unless major repair is needed.

    David, one of these days you need to make a bunch of sharpening videos for us too!!
    Andy

  13. #13
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    Quote Originally Posted by awestib View Post
    .

    David, one of these days you need to make a bunch of sharpening videos for us too!!
    This ^ !

    HH

  14. #14
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    With all this scientific evidence, I must be doing something wrong If I finish with edge leading strokes on a 1k stone I get a toothier edge, great for general use but will sometimes tear magazine paper. If I finish with edge trailing strokes on the 1k it has a cleaner edge and will push cut the magazine paper. Maybe I'm not using high enough grit stone, I've been experimenting a bit with the 1k recently.

  15. #15
    I've not been a fan of Dr. Verhoeven's evidence. Still, a careful reading of his paper states that a cleaner edge is obtained from leading edge sharpening. Your 700 level grit (American grit) is easily high enough to produce a whisper paper cutting edge. Merely spend more time on the stone at that level using a light touch and refine your technique then you'll see a better edge. A half dozen stones up to a zillion grit are not needed to produce a nice cutting edge. DM

  16. #16
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    bpeezer, are you using water stones? (guessing since you said 1k) And if so, how soft are they? I have noticed on softer stones and stones where i left too much swarf or slurry, that i'll degrade an edge more if i try to finish with edge leading. If i finish edge trailing, it will negate some of that effect.

  17. #17
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    Quote Originally Posted by fervens View Post
    bpeezer, are you using water stones? (guessing since you said 1k) And if so, how soft are they? I have noticed on softer stones and stones where i left too much swarf or slurry, that i'll degrade an edge more if i try to finish with edge leading. If i finish edge trailing, it will negate some of that effect.
    I'm using Chosera waterstones, they're fairly hard for waterstones IIRC. It's probably more my technique than anything else

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