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Single bevel vs Double bevel knives

Discussion in 'Shop Talk' started by Anton, Apr 4, 2016.

  1. The discussion on other forum mentioned that single bevel knives requires more skill from the maker to make. And the original question was about finding cheap stainless Deba knives. So I wanted to ask knife makers to share their wisdom on that topic.

    I don't see how it could be more difficult to make a single bevel deba, compared to gyuto. Yeah, the hollow part could be tricky to carve/grind/forge properly, but hey, it could be skipped competely! I mean it still would be a deba without hollow part on the back side. Yep, it would be boring to sharping, but it should perform pretty much the same way as a deba with proper hollow back side. Right?

    So the most straighforward way is to take a thick blank of stainless steel, cut the profile, grind main bevel, HT, polish, sharpen and call it a day. What could go wrong? What am I missing?

    Now let's imagine we want a proper hollow backside. And we could either forge it, carve it, or grind it. Depending on the chosen method, it could be a tricky to make properly. Unless you have a $$$ CNC milling machine :D

    To my naive eye it looks like here we might have additional problems with heat treatment. Probably forging should be performed much more accurately (if we choose to forge). What other possible problems do I miss here?

    So, again, overall I'm trying to understand what are the real difficulties in making single bevel knives that makes them harder to make. I can see why long yanagibas are tricky to make properly due to their hard hardness/warping. But I'm not sure why should it be tricky to make a deba or ajikiri or honesuki.
  2. Andre

    Andre Founding Member

    As someone who has used debas a lot I don't think they would perform as well without the ura. Part of why a deba fillets so cleanly, without tearing delicate fish, is that there is almost no friction as you make your cut. The fish is cut by the edge, sliding over, but mostly not touching the ura, and lifted and gently set down by the thickness of the knife.

    Without the thick spine and ura you have more resistance and potential to tear the grain.
  3. Em… clean slicing is what a yanagiba is supposed to do. And deba is mostly for rough butchering of fish. At least that's my assumption :)
    I've used Deba only once, so my own experience can be discarded, but lets look for someone who knows better then me. One of the first results on youtube gaves me this:

    Almost all the time the ura doesn't touch the filet at all! I mean even if you glue a piece of sandpaper to the ura, that guy would be able to cleanly butcher that fish. So far I'm not convinced that concave backside affects Deba performance. Any videos to show how wrong I am maybe? :)

    Thick spine IMO is done mostly to give Deba some heft and concave backside is to make sharpening easier, because sharpening without ura would require way more time. Well, at least that's what I think now :)
  4. Time to call Mythbusters
  5. Not sure on the monosteels. But I think san mai is very difficult as you only have cladding on obe side so therefore uneven stress developing during HT.

    Though for me the proof is in the pudding or what you get. You can get some great gyutos, sujis, petties etc at between $100 and $150 but there ain't many decent single bevels, or so i an told, in that range.
  6. Andre

    Andre Founding Member

    In practice you try not to pull the fillet up like that. On more delicate fish that tears the flesh.

    Rough butchering is for crappy butchers. All the cuts should be clean.
  7. Mrmnms

    Mrmnms Founding Member Gold Contributor

    Anton, I like the way you stir things up! Curious if most current single bevel knives are forged hollow or ground hollow on stone wheels or big wheel on grinders .
  9. Guys, I have to apologies for the initial negative/dismissive tone of this thread. I really shouldn't have posted it while I was in the bad mood.

    Most of us are knife fanatics here and we've learned a lot of things about knives by reading what others said and through our own experience. The sheer existence of this thread comes from a conflict between my own experience/assumptions and what I've read on the forums. I know that it's a tedious task trying to convince someone else, that he's not right, but please bear with me here.

    Initially I tried to address this thread to the makers, since they are the ones who can actually tell me in details whether it's true that single bevels are harder to make. And whether it's true for all single bevels, or just for some of them. And whether there are other things to consider.
  10. :)

    I'm really interested in this topic, since I have zero experience with single bevel knives, but would like to know what it's really about.
  11. Hey @Anton, For my money, Apart from using a thicker piece of steel (assuming) for the debras / Yanagibas the main consideration is how to achieve the zero edge/bevel on the belt grinder.
    I've always ground edge up, but I'm worried you'd shave the abrasive right off the belt at some point.... :( (exaggerated for effect). But I've always been looked at weirdly when asking about grinding edge down, which may be the way forward for this application?
  12. butch

    butch Founding Member

    i grind them edge up and finish them on DMT hones to make sure everything is even before goingot the waterstones
  13. Andre

    Andre Founding Member

    I did the same thing refinishing a coworkers abused deba yesterday. I did all the hard work on a 220 stone from the edge up, then used a JKI diamond 1k to make sure it was even. It is good to have something you know is mostly flat.
  14. butch

    butch Founding Member

    jjust to make note when i say grind im talking aoubt on my belt grinder single bevels are much more forgiving then a straight razor. so i get it close and then see where the hone marks fall and then go back to the grinder to clean up the uneven bits. sometimes i need to do this 3 or 4 times to get the edge ans even and as fine asa i can depending on the use usuba take the most care
  15. My attempts at making single bevel knives have been fraught with warpage, that's with two metals welded together.
    The key seems to be to find the sweet spot of pre vs. post HT shaping (grinding and/or forging), and preempting warpage and knowing how to deal with it; grind it out, or pre-bend the opposite way it will warp before HT, or know how much you dare try to straighten it post HT, or all of the above, perhaps other ways too?
    With a mono steel you could submit a symmetric blade to HT and then friend it to shape after, that might be very time consuming. With a bi-metal blade, there might be a problem grinding out the steel if one were to grind in a concave back?
    So, yes I think the single bevel is harder, or perhaps better to say it requires more know-how.
  16. The group of knife makers that I've been learning from always HT before grinding. Really does help with minimising warping and the VSM ceramic belts don't have any issues grinding hardened steel.
    If pre-grinding, I'd recommend doing a stress relieving treatment before you complete your main HT cycle, just to relieve the stresses within the steel.

    From what I've read elsewhere on single edge knives.... grind the Urasuki (hollow) in before the chisel grind. I guess this helps handling the blade later on.
  17. I have no real user experience but recently made a low deba I'm finishing up now. I quickly made it because I was running some small pieces of O1 in the oven..

    I don't know how good it is since I can only judge that the steel and heat treat seems to be good, and that it seems to sharpen correctly on the stones. So I look to get some feedback on it.

    Anyway, if it's close to good, it was easymode to me. I made it from 6mm Arne (O1) and rough ground pre ht and finish ground post, left about 1 mm edge during HT. Since I didn't have any warpage with this process it was pretty straightforward. Normalize, quench and temper...


  18. chefcomesback

    chefcomesback Founding Member

    I have made few monosteel single bevels and few clad ones , used deba often for couple years and use yanagiba 10-20 times a year ( obviously posted only few of the ones I made ) . Clad or mono They both possess different challenges compared to the double bevels in terms of making stages .
    When you think about traditional Japanese blades you also have think about their purposes and the reasons of the way they are made .
    Yes , you can skip the ura and have dead flat back side however most single bevels knives with ura are made for cutting things precisely without tear and to much damage to the texture . Having a hollow back allows you to have a steeper angle resulting cleaner cuts . With Yanagiba and deba this is Self explanatory .
    In terms of difficulty of making the single bevel the kata ha ( ni-mai) ones are more difficult to make , you have to forgeweld , draw in a way that cladding is consistent along the bevel and not to deep at the ura to reveal the cladding etc . It possesses another trick at the heat treatment too , if you use non low carbon cladding to a high carbon edge the blade bends like a Banana since the hardened steel moves and expands once it transforms to martensite while the soft cladding doesn't move . Historically Japan never was rich in resources and laminated knives were because of this necessity , they are easier to finish however they tend to move due to the different expansion rates of steel even at temperature changes . Jon had a good explanation in other forum a while ago about straightening yanagibas . I found double bevel San mai s are quite easy to fix if they are bend , fixing a ni mai yanagi wasn't that easy , required more precision , I was close to a flat ... One more bend close .. Then too much and fixing it back was lot more tricky ...
    You can definetely mill out the ura with Cnc machine but that's definetely something I am not interested in , I rather fail at straightening a honyaki on a wood stump with hammer than get a thick piece of steel heat treated and grind all day
  19. I am currently in the process of forging a traditional Yanagiba with a white paper edge and wrought iron cladding. I did the forge weld and drawing out with three layers (one thin WI/White/WI) to prevent it bending... Worked somewhat. Straightened it out during tempering and then went to the surface grinder to get rid of the thin layer of wrought. The resulting heat from grinding was enough to warp the blade like a dead fish... Will see how it continues... Already told the client that there might be a monosteel backup blade with a nice hamon if all else fails.

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