Burr/wire edge?

Discussion in 'Maintenance, Tinkering & Embellishment' started by Masibu, Dec 9, 2018.

  1. Masibu

    Masibu

    12
    Dec 8, 2018
    Alright, massive first post with lots of questions/thoughts but bare with me. I sharpen mainly chef knives/slicers/paring knives and have consistently had issues maintaining a "shaving sharp" edge for any great deal of time (predominantly with larger knives). I have both carbon steel knives and various stainless in a range of rockwell hardness from both Japanese and Western makers alike (mora, victorinox, aus 8, aus10, ginsanko, and sg2 among others). Whilst they maintain working sharpness they become noticably duller after fine slicing only a few bunches of shallots or similar (will still cut but sharpness has degraded by a fair amount). I've spent months trying to figure out the root cause of this. Here are some details about how a general sharpening session would be (I'll include the initial sharpening of a new knife or a knife with unknown edge geometry)

    Lets say im about to sharpen a 61 rockwell ginsanko chef knife that is 50mm wide at the heel and 250mm long (similar approach and results with my carbon gyutos as well). I'm free handing and raise the spine of the knife about 5mm off the stone at the heel to set a bevel (this would be around 6 degrees per side?) And typically finish at like 12mm off the stone for the micro bevel (this would be around 13 degrees per side?). My terminology may be incorrect here but those are the angles im using anyway. I typically use back and forth or scrubbing strokes in initial shaping of the edge and move to heel to tip strokes in subsequent sharpenings and when I'm close to finishing a knife

    (New knife)
    - destress lightly on a flat soaked cerax 700 (or 320 in the case of severely dull knives)
    -grind right side until edge stops reflecting light
    -lightly destress twice on the same stone again
    -grind the left side until the edge stops reflecting light

    I pay attention here to whether one side has stopped reflecting light sooner than the other and by roughly how much quicker this process has occurred. As Japanese knives are generally assymetrically ground and sharpened often the right side will be finished much sooner than the left. It's at this point I'm unsure whether to:

    -raise the angle on the side that took longer to prepare to account for the assymetry of the blade (and potentially lower the angle on the side that was prepared sooner) to keep the grinding times relatively similar per side

    Or

    -keep at the same 50/50 angle and grind more on the side that took less time to prepare so that the edge eventually moves closer to the side that originally took longer to prepare, eventually resulting in similar grinding times per side. (This process tends to involve a constant destress and prepare cycle keeping the number of passes per side needed to prepare each side in mind). This can take a while to even out in some cases

    Whichever route I've opted for I now know for future sharpenings what angles are required for even grinding on each side. After that initial bevel setting or if I'm touching up that knife after use in the future the process is then:

    -destress once lightly on the stone
    -grind each side of the blade evenly until the light stops reflecting (This tends to happen rather quickly with decent 300-700 grit stones).
    -I will typically make a bit of a slurry on the stone with a diamond plate or nagura and move to alternating heel to tip strokes trying to change the scratch pattern each time. These are made edge leading to reduce the chances of forming a burr (the slurry/mud helps with this). This may typically be about 8 or so per side. Blade slices well at this point and in the case of finer grit stones it may shave also at this point
    (Although not important)
    -clean off the stone or grab a finer polishing stone
    -raise the angle to 13 degrees per side (or in the case of the assymetrically sharpened blade ~8 degrees one side and ~16 the other) and use alternating edge trailing strokes crossing the patterns again to reduce the likelihood of another burr forming. This is typically only around 2 each of heel to tip and tip to heel strokes on each side (In the case I decide to go with an 8k finishing stone I will usually use double these angles however typically I will use a 3000 grit stone). The blade will usually shave ok at this point
    -use the same edge trailing strokes at my original shaping angle to "backbevel" and reduce the effect of any 'blunting' the micro bevel bas causes. This can be anywhere from a couple of strokes to like 15 per side. Blade usually shaves even better than previously (although i dont think I've ever been able to get tree topping sharp that people describe. Even my gold dollar straight razor that I use for shaving doesn't do that although I find it fine enough to do the job without any irritability)

    At this point I'm pretty confident ive produced a wire edge here despite the apparent keenness. To elimimate it ive been playing around with:
    - trying another light edge leading microbevel pass or parallel to the edge. I have also tried doing this with the original shaping angle. As the majority of my sharpening stones are friable waterstones its pretty easy to trash the edge with an edge leading pass without improving it. Using higher grit and harder stones help slightly.
    -alternating an edge leading pass at shaping angle on each side on my norton fine followed by alternating trailing passes on a finishing stone (3 or 8k)

    I have tried other stones and approaches but overall the blade has felt pretty similar in use at this point.

    -There is no light reflecting on the edge, the knife feels to cleanly cut paper and can usually perform a 90 degree push cut on paper pretty easily.
    -In the case of the assymetrically sharpened/honed blade it will typically shave at a lower angle on the side with the lower angle applied (generally the right side) compared to the other.
    -The 50/50 blade will shave reasonably evenly on both sides.

    At this point im happy enough to use the knife and within 5-10 minutes notice slight dulling occurring. I get the light out on my phone and scan the edge again and typically there will now be light reflecting off the edge in areas that feel blunter than others. This typically happens more closer to the tip of the knife but will appear in sections of the blade. I have tried honing just the microbevel til the light fades as well as that plus the back beveling and it never stabilises. If i continue on the microbevel for too long it just thickens the edge without improving cutting ability and just makes the next sharpening job more time consuming on the knife.

    From what I gather the angles im using are lower than what generally gets recommended but even at "normal" angles the same issues arise so I've continue doing what I'm doing so my edges at least remain thin and cut decently until I figure out exactly what is happening. I should also mention that at work we use poly boards that aren't perfectly flat so I havent ruled that out as a possibility yet. I am going to try another board tonight to see if that makes any discernable difference.
     
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  2. Masibu

    Masibu

    12
    Dec 8, 2018
    After coming across scienceofsharp I will eventually get some kind of strop to see if that makes a difference however I have a llama brand kanayama strop i bought with a kamisori years ago- would using that bare be enough instead of creating some kind of strop and whatever equivalent metal polish i can find here in Australia? The linen side is fairly rough but would it be enough to remove any small wire/burr that remains on a blade whilst introducing microconvexity?

    Throwing a spanner in the works, more recently I came across a 90mm misono swedish carbon paring knife I sharpened months back without any real thought process and decided using it again. Whilst I don't do any extreme cutting with this knife ive found that the shavability of this knife to have held up incredibly well. I tried doing board work with it, using it with extra force than necessary and it still holds up without any light reflecting at all and shaves easily. Being that it was so long ago that I sharpened it I can't even recall if I did anything different than normal that may have caused this to occur (annoyingly I didnt write any notes like I have been with my chef knives so I can figure it out).

    It got me thinking how that a heel to tip (or tip to heel) pass on such a short knife would result in scratch patterns that are "straighter" (is perpendicular the right word here?) And with more narrow "x" grinding lines than on a 250mm chef knife on the same size benchstone. If I were to sharpen a knife with scratch patterns running parallel to the edge i imagine the edge retention would be horrible by comparison but does having scratch patterns than run more perpendicular increase edge retention? I will probably try to do this with my chefs knife somehow just to see if it does anything (im guessing by avoiding heel to tip strokes and doing back and forth strokes of the knife in sections).

    Few more questuons..one regarding assymetry.. am I more likely to see this type of dulling occur in an assymetric blade than on a 50/50? I haven't yet noticed a great deal of difference in either approach to different assymetric blades. I do like the way assymetrically sharpened blades cut food although it's just made it seem more complicated in trying to fix this issue in terms of how do I stabilise the edge (do I need to raise the angle on a certain side more than the other/do i need extra strokes per side etc) so I've shifted my focus to 50/50 blades first.

    The other question.. when using the light to check the edge and I notice the light reflect after use is there a discernable way for me to tell whether its a result of microchipping or just dulling? I've raised my angles to see if the problem disappears but it hasn't seemingly made any improvements at all (worse if anything) so I've just kept doing what ive been doing.

    I really wanted to try to figure all this out without a microscope but it might make it a bit more obvious where I'm going wrong.
     
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  3. bgentry

    bgentry

    Aug 3, 2009
    I've long struggled with how long an edge is "supposed" to stay shaving sharp when using it for real world tasks. I have a few blades with "super steel" that only seem to perform marginally better than more "regular steel" blades, in terms of retaining a very high degree of sharpness.

    I find that just a little bit of real world work dulls the edge enough to either not shave hair or go from say phonebook paper push cutting sharp, down to phonebook slicing sharp.

    It's hard to say if my experience is due to the realities of steel and blades, or if it has something to do with my sharpening technique. In other words, *I* might be the problem. I'm not sure.

    I can tell you for sure that cutting force, media you are cutting, and the backer (cutting board) all make a big difference. If your "poly" boards are hard plastic, they are kinda hard on edges. If you were cutting very hard material, like gourds or similar, I would expect rapid dulling. Also really abrasive media like cardboard is pretty hard on edges. I find cardboard to dull edges from shaving to "not impressive" in only a few feet of cutting. Maybe 10 feet? Likewise if you are "slamming" the knife into the board as you cut through things, that will dull the edge much faster as well.

    I was going to offer some more guesses, but I think I'll defer to other more knowledgeable members on this one.

    Brian.
     
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  4. David Martin

    David Martin Moderator Moderator Gold Member

    Apr 7, 2008
    a bgentry quote,"super steel" that only seem to perform marginally better than more "regular steel" blades". Yes, agreed.
    The super steel (s90v) performs way better than 420 then about 40% better than 440C and marginally better than something like cpm154 steel.
    Just my findings. Much is marketing and the cost is twice what the others would be. 2 good blades of 440C would out cut one of s90v and
    cost about the same.
    I use the poly boards for a backing while cutting meat and I've used plywood. They both will degrade an edge and little items like this will
    be noticed at the end of the day. Just regular use of cutting force will indeed curl the edge on s90v. DM
     
    Last edited: Dec 9, 2018
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  5. Masibu

    Masibu

    12
    Dec 8, 2018
    I've always figured that these edges aren't "supposed" to stay that sharp for very long but after browsing through various forums etc I've come across claims of various blades/axes maintaining "shaving sharpness" long term or that a mirror polished edge "lasts longer" so I'm trying to discover for myself how realistic these claims are and whether I can replicate the same for myself.

    I fully agree that "super steels" can be nothing more than marketing hype and that sharpening angles play a much larger role. Some of these so called "super steels" fail at holding acute angles and ironically have to be kept at less sharp angles to perform whilst also being slower to grind and then requiring more care to prevent damage occurring. Knives are used for simple tasks, super alloys dont help with those purposes in mind.

    The plastic boards we use are fairly dense compared to wooden boards however we aren't supposed to use them in a working environment unfortunately so I only have my board at home to compare (and food preparation is far more limited comparatively to be able to conclude that its purely the boards im using alone that is having the most detrimental effect.
     
  6. wootzblade

    wootzblade

    228
    Feb 24, 2014
    Last edited: Dec 9, 2018
  7. I've also been wondering about the cutting board. If the 'poly' cutting board is one of those harder ones, like Brian mentioned, that may be an issue. I've seen some of the harder ones in stores more recently, and I've shied away from buying them.

    On the other hand, I've been using some older white 'poly' cutting boards, purchased 15 or more years ago, that are pretty soft. They're the ones that may've had a bad rep for easily scoring or leaving cut marks all over them, which some say will trap & hold bacteria & such (I've never had an issue with this; just clean them thoroughly after each use). But the one upside is, they've never damaged even my low-end, soft stainless kitchen knives that I've thinned to < 25° inclusive or so.

    Awful lot of things could be going on. Starting out, in order to narrow it down, I'd suggest an 'extreme de-complication' of the process. Nothing fancy with a mix of stones or technique; just take each knife to ONE stone, apexing the edge to a verifiable burr (no assuming or guessing allowed at this) to be cleaned up, and then testing how each cuts, and for how long. Beyond that, change one variable at a time, and test again. Too many variables right now, in the described process, to draw any meaningful conclusions about where something may be going astray.

    It may also just be an issue of expectations set too high, i.e., if retention of true shaving sharpness is expected after some use. Some steels just won't do that reliably anyway. I limit most of my sharpness tests to slicing and/or push-cutting paper consistently, which most decent steels can do well enough after non-abusive kitchen cutting tasks.
     
    Last edited: Dec 9, 2018
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  8. Wowbagger

    Wowbagger

    Sep 20, 2015
    I love long posts but haven't woken up enough yet for all that so I didn't read your entire post. I did scan it. You get the knife sharp and then it gets dull very fast.
    You know how to sharpen. Right.
    The knife gets dull very soon after using it a little tiny bit on some non abrasive vegetable matter. Right.

    I have two words for you :
    Cutting Board

    See this Link>>>>> and page down to the latter part.
     
  9. Eli Chaps

    Eli Chaps Gold Member Gold Member Basic Member

    Apr 20, 2018
    This is good advice for sure. Raise a burr on one side, then raise a burr on the other. Then single strokes per side. See what ya got.

    That said, it's difficult to maintain a shaving-sharp edge when cutting on a board, even the kinds ones. Dragging the edge across the board to scrape ingredients to the side will also dull that keen edge. Cant the knife over when doing this to more closely approximate some angle rather than more vertical. I hope that makes sense.
     
  10. Masibu

    Masibu

    12
    Dec 8, 2018
    Some excellent suggestions here, i wasn't expecting feedback so quickly. Looks like ive got some more reading to do. I have tinkered enough with my approaches to how I've been sharpening and kept using the same board as a control so I think its time to change that up and see how big a difference that makes.

    I dont use my knife to scrape and try to limit the amount of force and movement on the board although the tip definitely sees more board contact than the rest of the blade. I untrained myself out of that bad habit once I started using harder japanese blades. I wouldn't be surprised if the board is a big part of the issue. The boards are textured as well come to think of it (where it hasnt been worn down from the years of use)

    If the board does end up being the problem would setting the bevel at higher angles/thicker edges compensate for this? (was thinking maybe 30 degrees inclusive). I'm leaning towards "no" here as it doesnt seem like the edge is chipping at all - it's just wearing quickly.
     
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  11. Gday mate

    Gday mate

    8
    Jan 16, 2018
    Do you use a steel to maintain your edge throughout the day on the softer knives?
     
  12. Masibu

    Masibu

    12
    Dec 8, 2018
    If im using softer blades I would use a regular cut steel throughout the day as its the only steel I still have. I no longer own a polished steel as i sold it off years ago when I first got into sharpening; thinking at the time that harder japanese blades were better than what I was using previously and that stones were the go for maintenance. I've thought about getting a ceramic steel/strop for my harder blades and a polished steel for the softer ones but I'm not so keen to splash the cash just yet so im making do with the stones I have (which is admittedly quite a lot as it is) and using cardboard as a strop.
     
  13. SuckSqueezeBangBlow

    SuckSqueezeBangBlow

    43
    Apr 23, 2017
    I have a tojiro chopping board, it's extremely soft timber and very light. Edges last much better than using hardwood lol
     
  14. larrydallas

    larrydallas

    3
    Dec 8, 2018
    I'm not a professional chef, I just cook at home, so I don't like to pull out stones just to hone. I hone the Japanese knives with a strop when they're sharp and steel when they start to get a little dull. I use a polished smooth steel on softer stuff, like vg-10 or my K-Sabatier but it doesn't work for super hard steels. For those, I use an Idahone fine ceramic steel. The only knives that touch a regular grooved steel, like what comes with a knife set, are the super cheap knives from the Chinese supermarket. A lot of Japanese knife enthusiasts swear by the Hand American borosilicate honing rod, but they always seem to be out of stock and they're really expensive when you can find one.

    These knives don't get the kind of abuse a knife takes in a professional environment, but they get used every day. I probably put them on the stones every couple months.
     
  15. Gday mate

    Gday mate

    8
    Jan 16, 2018
    Working in the meat industry I put my knives on the stones the night before work every day, when I get to work the next day I steel the knife I will be using on my smooth steel and get to work. I steel it as often as I can, usually 3 passes each side (probably once every minute or two) until the smooth isn't bringing it back any more. Then I put it on my regular cut for 4 to 5 passes each side followed by the smooth again. From what I can tell my edge is more polished off the stones then off the regular cut, which is why I follow it with the smooth, and start on the smooth in the morning. There is a big difference in the finish between the regular and smooth. If I need to use a ceramic I go, ceramic, regular, smooth.
     
  16. Masibu

    Masibu

    12
    Dec 8, 2018
    Im actually considering starting a butchery apprenticeship next year. What stones do you use for your butcher knives? I usually use a norton coarse/fine combo but im curious as to whether there would be any advantage to polishing any higher than that, particularly if using a polished steel for maintenance.

    Do you use roughly the same angle on the stones as the steels or do you use a higher angle on the steel (like a microbevel of sorts)?
     
  17. bucketstove

    bucketstove

    Sep 23, 2014
    Hi,
    about how much pounds are you pushing down when sharpening?

    that edge is reflective on food after 5min , it hints burr, so first thing to rule out is remaining burr folding over
    as edge trailing promotes burr creation,
    try edge leading ,
    use two times one pass per 35-45 degrees per side, ultra light,
    to remove burr
    then five times one pass per side at 13 to 15 degrees per side
    and repeat as needed after
    a few cuts in paper
    a few in wood
    then check for reflection, if it shaves in both directions, if it still push cuts paper...


    if using muddy stone flush the mud
    if its not working on soft/muddy stone, try a harder stone
    if you dont have a harder stone try bottom of a coffee cup


    repeat a few times and report back



    Also consider this mind exploding material , spyderco delica/pacific salt...Extreme Regrind , ~6DPS no damage in 50 slices into pine, hardwood flooring and plywood the edge eventually gets damaged while cutting metal (steel food can)
     
  18. Masibu

    Masibu

    12
    Dec 8, 2018
    I generally apply around 200g (1/2 pound?) When sharpening- more if its a heavily dulled knife that needs a lot of work. After the edge stops reflecting light I go as light as I can (estimate is maybe 50g or so) with edge leading strokes to reduce any burr, same again with the micro bevel.

    I finish with edge trailing strokes if im using water stones as it's generally more difficult to apex edge leading with friable stones without dulling the edge. My norton coarse/fine combo I can do edge leading with easily but my next hard, fine stone is a shapton pro 5k (excluding a couple of naturals). I can try using my harder stones but I'm still determined to get results with my softer stones as well if only to develop my skills with them.

    I'm sure I've tried that high angle approach before a few times and not gotten any improvements (reduced sharpness) but I'll try again. It's reading through pages such as that one that is driving me to perfect my sharpening skills
     
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  19. Gday mate

    Gday mate

    8
    Jan 16, 2018
    I use the dmt diamond stones from course through to eef and a hard Arkansas. I usually only use the eef and the ark daily though. I use the course plate for rubbing back shoulders and reprofiling usually once a week. Most guys at work use the norton stones provided by work at work in the morning, but they are really glazed up and I'm sure they polish beyond their grit rating. I sharpen my knives at 10 deg each side and steel at probably 12 or 13 deg on average. Hope this helps.
     
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  20. Masibu

    Masibu

    12
    Dec 8, 2018
    So doog, that is helpful. I wouldn't have thought to refine the edge that high myself. I haven't got a hard ark but I do have a few polishing stones which should come close. The norton does seem to cut much finer when it's glazed up, I tend to view mine as more of a 700, higher if its really glazed.
     

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