What edge angle is good for supersteels

Discussion in 'Maintenance, Tinkering & Embellishment' started by wootzblade, Jun 6, 2020.

  1. wootzblade

    wootzblade

    240
    Feb 24, 2014
    They do, but it is not all that straightforward.
    At meat plants optimized for best performance, they sharpen knives to a lower edge angle.
    As knife brands are not equal, not all hold the low angle edge well, so it is not necessarily the 12 dps.
    Boning butchers commonly use knives of 11-12 dps.

    Look, at the plant there are 100 boners that have been cutting with 15-18 dps knives since their apprenticeship, for many years.
    Give them the best performing knife sharpened at 12 dps, and you will disrupt the process. They will tell you that the knife "clings to the bone" and refuse it, and even if all your indicators show good, this cannot change years of habits... And if we disrupt the process and cause losses, our consulting business is doomed.

    The management' willingness to optimize, habits and legacy of the past, concepts in the head of the plant trainer, the way they steel, grinding and honing equipment they already have and whether they are willing to upgrade, staff re-training - all that matters.

    In commercial kitchens it is chiefly portioning cuts, they load knives differently than boning. In kitchens the middle and heel sections of the blade carry the main load. While in boning where many cuts are done with reverse grip, the tip half of the blade carries the main load. Meat plants and butcheries require very sharp knives that dull mainly from rolling; though knives are sharpened daily, they are relatively easy and quick to resharpen. Commercial kitchens are happy with "working sharp" knives, and the edge that we get from them is abraded off by the hand-held pull-through "sharpeners" they use to "maintain" the edge; sharpened once in 3-4 weeks and require full regrind.

    In my Knife Deburring book you can read about all common knife steels, and see our sharpening protocols for them, including the VG10. Sharpness in BESS, sampled in the sharpening protocols is from real sharpening sessions. If you cannot see your knife steel in my book, email me and I will be more than happy to give you our protocol for that steel - you can adapt it to the sharpening equipment you have.
    Testimonials: http://knifegrinders.com.au/Book_Testimonials.htm
     
    Last edited: Jun 17, 2020
  2. Barmaley

    Barmaley

    167
    Dec 31, 2016
    Vadim, I understand that you finish your blades on a paper wheel. According to very first sticky on this forum about paper wheels sharpening on them soften the edge because of overheating. So, you may get a very sharp edge but it will not last long. May I ask you to comment on it?
     
  3. Mr.Wizard

    Mr.Wizard

    Feb 28, 2015
    @Barmaley I believe he only does final honing/deburring on paper wheels, probably lightly and quickly enough to avoid heat problems. His testing is extensive so if the edge did not last long he would know about it.
     
    Last edited: Jun 18, 2020
  4. kwackster

    kwackster

    Dec 23, 2005
    [​IMG]
     
  5. Mr.Wizard

    Mr.Wizard

    Feb 28, 2015
    To whom is this a response?
     
  6. kwackster

    kwackster

    Dec 23, 2005
    @Mr.Wizard :
    It wasn't you who i had in mind, ;)
     
  7. wootzblade

    wootzblade

    240
    Feb 24, 2014
    Overheating of the very edge is a risk. We've experimented with paper and felt wheels to minimise that.
    As a result, I've replaced full-speed buffers with half-speed in our workshop, and we use only slotted wheels that cool the edge like fan as you hone.
    I know that kwackster also uses a half-speed grinder, and people who write to me tell us that they use either variable speed or half-speed buffers/grinders for knife honing & deburring.

    http://knifegrinders.com.au/SET/Effect_of_felt_and_paper_wheel_on_edge_retention.pdf
     
    Mr.Wizard likes this.
  8. 000Robert

    000Robert Gold Member Gold Member

    Mar 28, 2020
    That is what I understood from my research on the paper wheel system also. So I decided against going that route.
     
  9. HeavyHanded

    HeavyHanded

    Jun 4, 2010
    I cannot imagine top end speed makes a difference in terms of heat buildup. IIRC Richard J recommended more speed with slotted wheel, not less. As an example, my HF at about 475 rpm is still passing over 20 ft per second, and that's barely moving. I get best results on powered belt running fullout 3400 rpm and if it went faster I'd run it faster.

    Am no expert by any means as I mostly finish by hand or occasionally on leather belt, but I do know that running my grinding belts at higher speed decreases heat buildup by grind time, as long as the belt is in good condition.
     
    wootzblade likes this.
  10. razor-edge-knives

    razor-edge-knives Moderator Moderator Knifemaker / Craftsman / Service Provider

    Apr 3, 2011
    It looks like in the study there is a fair amount of 'scatter' so it's difficult imho to make some conclusions. I also may have missed it, but how many cycles/tests were done at each angle, and was there anything done to prevent any type of bias? (not that you intentially had bias, that's not what I'm saying, it's just that we all have thing that can influence 'how' we test).

    Some things are confusing to me. For example, below you have the intial sharpness then the sharpness after 1 cycle.
    • There are multiple instances in both charts that have higher BESS scores, then lower, then higher again. So for one example: in the initial sharpness chart with S290 we see '72' at 20 dps, then it jumps down to '64' at 17 dps, and back up to '72' at 15 dps before going down to '60' at 11 dps. And in the 1 cycle chart, S290 goes from '210' at 13 dps, to '162' at 12 dps, back up to '213' at 11 dps. I would expect to see some consistency be established the more runs that were done and the scatter is reduced.
    • Were the two side by side numbers for D2 and X50CrMoV15 two different tests at those angles? If so this also shows what I'm saying, just taking two different tests even at the same angle can reveal a large difference in scores.
    • For the same two steels listed in the point above, the scores at 10-11 dps from the 1 rolling cycle vs the initial sharpness didn't really change and is well within what I would call the 'scatter range' (not sure of the correct term, maybe 'scatter variability' or 'tolerance'). But what we would expect to see at these low angles is a weaker edge that shows a significant sharpness reduction due to rolling. Why is there practically no difference?
    [​IMG]
    [​IMG]

    I may be wrong, and this is only what I suspect (would be interesting to examine what's going on under SEM). For the D2 at low angles I would think there is something going on with the large carbides causing the initial sharpness numbers, and for the X50CrMoV15 probably some form of a wire edge. What are your thoughts on this? I saw where you say "Combination of these two opposed forces: the light rolling of the edge, and the low edge angles, gives the seemingly chaotic sharpness scores that we see at 11 and 10 degrees." however that would not explain the initial sharpness weirdness.
     
    Mr.Wizard, Barmaley and Eli Chaps like this.
  11. razor-edge-knives

    razor-edge-knives Moderator Moderator Knifemaker / Craftsman / Service Provider

    Apr 3, 2011
    I did not see any explanation on page 15 about why meat plants don't use a ceramic rod? The ceramic rod works fine for high carbide steels - I've used it on m4 at 68rc, along with 10v at 64rc with no issues.
     
    Barmaley likes this.
  12. sickpuppy1

    sickpuppy1 Gold Member Gold Member

    847
    Sep 27, 2018
    From page 15.....
    Though they look quite similar, showing an improved apex and micro-bevel, the traditional steel does it cleaner, while the ceramic rod creates scuffing on both sides of the edge. Ceramic rods remove metal by abrasion, while fine-cut steel ribs are smooth and they increase rate of metal removal by reducing the contact area and increasing the local pressure rather than abrasion; ceramic rods produce scuffing and microburr, while steels hone burr-free - and where the presentation cut is important, traditional steels are preferred.
     
    razor-edge-knives likes this.
  13. razor-edge-knives

    razor-edge-knives Moderator Moderator Knifemaker / Craftsman / Service Provider

    Apr 3, 2011
    Ahh thanks I must have missed that last sentence. That is very interesting because it seems like the ceramic rod produces a keen and clean apex. I wonder if any blind studies have been done to show that there actually is a noticeable difference in the presentation cut between the two.
     
    Eli Chaps likes this.
  14. Zeunerite

    Zeunerite

    50
    Dec 24, 2019
    I wonder how AEB-L would perform in these tests. Retains a good level of toughness above 60rc and has a very low carbide content so it should respond well to steeling.
     
    Barmaley likes this.
  15. wootzblade

    wootzblade

    240
    Feb 24, 2014
    That is what we see as well, at high RPM the long belts are way better than wheels and short belts, and coarse grits are way better than fine - long belts of coarse grits have less overheating risk than wheels, and practically none if run with a water mist.
    It is wheels and short belts, and fine grits that may cause overheating.
     
    Last edited: Jun 19, 2020
  16. wootzblade

    wootzblade

    240
    Feb 24, 2014
    @razor-edge-knives
    Would you trust a data that look overly consistent? I would not. Live numbers always come as a scatter, and we take the data set and look for tendencies and what falls out of the tendency, to draw our conclusions.
    For example, take this experiment: 1 rolling has too much of a scatter to make conclusions, but it is interesting in itself as to how badly even little rolling of the edge apex can drop sharpness even in supersteels. Looking at the 1-rolling numbers, I better understand the role of rolling in dulling.
    I did 5-cycle rolling in all edge angles, but differences between the steels are too small to be convincing, and I did not include that data in the report.
    100-cycle rolling is good - we see distinct tendencies.

    I've read through the posts on this page, and honestly cannot say more than I've already said in the conclusions - it may be better worded than in the video: http://knifegrinders.com.au/SET/What_Edge_Angle_Good_for_Supersteels.pdf

    Appreciate everyone's comments.
    As to the ceramic and diamond rods, none are used by boning butchers and at the meat/poultry/fish plants. I guess it may be because of the foreign particles coming into the product from the rods and abraded blades - but this is only my guess. It may simply be a matter of tradition and legacy, I don't know.
     
    Last edited: Jun 19, 2020
    razor-edge-knives likes this.
  17. HeavyHanded

    HeavyHanded

    Jun 4, 2010
    This is what I see as well but only when applied pressure is the same. If grind pressure is perhaps just enough to maintain good contact, when using the belts at high speed the pressure should be just enough to maintain contact along high points. Running at a lower speed the tendency is to use more contact pressure, even if it is still very slight. At high speed the blade shouldn't even be making constant contact. I plan on doing a bit more with the paper wheels coming up, but is not a priority.
     
    razor-edge-knives and wootzblade like this.
  18. Barmaley

    Barmaley

    167
    Dec 31, 2016
    It is in direct proportion with number of tests on a run. At a certain points data will get very consistent provided that correlation is high; if the correlation is weak then the value of scattered data is low as well I guess...
     
    razor-edge-knives likes this.
  19. Barmaley

    Barmaley

    167
    Dec 31, 2016
    Vadim,

    I just bought and read half of your wonderful book "KNIFE DEBURRING". There are many questions but A) it does not make sense: you recommend sharpening M390 at 13 Dps which seems to contradict to the main point of your research!!! It will be also very interesting if you could elaborate in VG-MAX and its 16 Dps o_O . In addition Burrfection at some of his youtube videos claimed that during the visit of the factory in Japan which makes those steels there is not serious difference between VG10 and VG-MAX beside that VG-MAX is not sold to China and a sales gimmick. Is this forum or thread appropriate place to discuss your book, which I highly recommend to everyone?
     
  20. wootzblade

    wootzblade

    240
    Feb 24, 2014
    Thank you for paying for the book, hope you also find it worth the cost of 2 Caffe Lattes as one of our readers said. I really appreciate it, we are now in the middle of 2 projects: speeding up the Tormek RPM, and manufacturing rock-hard felt wheels for deburring on Tormek, and every stream of income to fund them matters.

    M390
    You are talking of examples for our sharpening protocols in the Appendix II.
    All examples are taken from our real sharpening sessions, and you can see there edges sharpened at 10, 12, 13, 15, 16 dps. We do not always sharpen knives to an edge angle that we deem the best performing - sometimes it is by the customer's instructions, sometimes, especially with smaller folders, we cannot go too low because of the knife design.
    I give the edge angle the knife was sharpened at in every example, because the angle effects results in sharpness tests - so that the readers with a BESS sharpness tester could follow our protocols. Not because I think that the angle in that example is the best edge angle for that knife steel.

    SHUN VG-MAX
    SHUN knives almost always come chipped to a sharpener, and I repeatedly saw its apex chipping during grinding on #160-200, when we ground them at <= 14 dps. We grind edge-leading. So we decided to stick with the manufacturer's recommendation of 16 dps. At 16 dps SHUN does not chip, well at least not during grinding.
     
    Last edited: Jun 20, 2020

Share This Page