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Jun 30, 2014 09:16 PM

Akifusa Santoku 180mm - microchipping on edge

I have an almost brand new Akifusa santoku 180mm - my first "real knife." I've used it maybe 5 total hours and cut only vegetables (nothing harder than a carrot). I've been using a bamboo cutting board.

After cooking last night, I noticed some microchips on the edge, about an inch down from the tip of the blade:





In case those embedded images don't work, here are the direct links:

From Akifusa's website, "the san mai powdered metallurgical (PM) steel blade is similar to a Western Chef knife with the cutting qualities of the best Japanese-made knives. PM steel is created using a crucible technique and results in smaller grain structure and significantly longer edge holding. The center layer is SRS-15 PM stainless steel originally designed for metal cutting tools. It was hardened to Hrc 64 and is clad on the sides with soft SUS-405 stainless steel."

I've tried to cut really carefully -- unfortunately I have used the knife edge to scoop chopped veggies and have also rock chopped with pivoting to mince herbs (cross chop?).

I have been honing the knife carefully with a ceramic honing rod, keeping the angle consistent with about the width of a matchbook from the steel.

So, questions . . .

Is the micro-chipping to be expected with this knife? Or is it entirely due to probably poor technique or habits on my part? Finally, is it "safe" to use the knife in the meantime (for the blade, mostly), or do I need to get those chips sharpened out immediately? Finally, are those chips small enough that they should sharpen out no problem?

Thanks for your thoughts!

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  1. Most important answer first: yes those chips are small enough that they should sharpen out with no real problem.

    Also, you do not necessarily need to get the knife sharpened immediately, though it depends on your preferences.

    As for what's causing the chips... that's a little tougher.
    - The bamboo cutting board may not be causing the chipping, but it's certainly not helping either. Hardwood cutting boards are noticeably easier on a knife's edge.
    - Rock chopping doesn't necessarily cause chipping, but rock chopping with too much force and a sloppy motion can. With Japanese knives, you generally need to have a 'cleaner' stroke than you do with Western knives, since the profile of the blade doesn't guide you and the edge itself is both more sensitive to lateral strain and often sharper therefore biting more deeply into the cutting board with comparable pressure.
    - It's possible to chip a knife while honing it. If you have been careful and gentle then that's not the likely cause, but it's still worth a mention.
    - Dropping it on the floor or in the sink or letting it bang around with other utensils can also cause chips, but I get the feeling this is unlikely in your case,

    Finally, 64 hrc is fairly hard, powdered steel or no. With a low enough edge angle, the blade can be made to chip no matter what you do. The trick is to find the sweet spot in terms of an edge that works for you without chipping but still cuts as well as possible.

    As I said above, the very small chips you have aren't a huge problem and aren't hard to fix - they're just showing up awfully fast. If I were looking to fix the problem, I'd address any potential issues I mentioned above first, maybe get a wood cutting board if budget allows, and see if more chips develop. If they do, I would likely start by resharpening the chips out using the factory angle and then trying a microbevel on the edge. If that was unsatisfactory in terms of either performance or continued chipping, I'd start walking the edge angle up, looking to find the lowest edge angle that alleviates the problem. I do my own sharpening though, so if you rely on a professional, you might have to either fork over more money than you'd like to dial it in or else just ask the pro to go several degrees more conservative right from the first sharpening.

    8 Replies
    1. re: cowboyardee

      Thanks for the advice, I'll invest in a better cutting board right away. I purchased the knife from epicurean edge so I'll take it back to them too and see what options there are for sharpening those chips out and possibly adjusting the angle.

      I'm used to dull crappy knives so I'm probably cutting with way too much force when mincing garlic and/or herbs. I've tried to use a gentle push cut with a bit of forward motion for most cuts, but it's that hard mincing with my right hand on the handle and left hand on the spine near the tip while pivoting the blade laterally that worries me.

      Unless I've just been honing incorrectly, like you suggested is possible. So many variables . . .

      Anyway thanks again!

      1. re: jacobrb02

        In addition to what Cowboyardee (spot on…bro!) said, it’s not uncommon to experience micro chipping with new high HRC knives. A momentary lapse with powered sharpening / buffing machines is enough to overheat the edge. The issue should resolve itself after the first or second hand sharpening.

        In general, microchips (that occur all along the edge) is likely due to honing or steeling. Although honing a soft HRC edge is normal, honing a high HRC edge is unnecessary and conducive to chipping. If you need to do it, do it very gently and use one that is smooth (Borosilicate / Glass).

        Microchips (that only occur at the belly of the edge) is likely due to rock-chopping with too much downward or lateral force. That two handed power rocking, walking the blade from side to side will easily cause chipping because it’s very difficult to not torque or twist the blade while the edge is embedded in the cutting board. I more or less only rock-chop when mincing herbs, and will make a concentrated effort to not push down too hard, or walk the blade.

        Hang in there, it takes a little awhile to get used a high hrc blade.

        1. re: JavaBean

          thanks for the advice - is it okay to use ceramic very gently to hone?

          1. re: jacobrb02

            Yes. It's not strictly necessary, but gentle honing with a ceramic at the correct angles shouldn't cause any damage. Grooved honing steels are more likely to cause damage with your kind of knife (and more or less unnecessary also), but a ceramic rod is fine if it's used well.

            Some people do switch over to using strops as maintenance in between sharpenings for harder Japanese knives. You can easily make one yourself. Others don't use strops or honing rods but touch up Japanese knives frequently on medium or high grit whetstones. Any strategy of the three can work well.

            1. re: jacobrb02

              You should be ok, but using a ceramic hone ( ~1k or 2k grit) on your knife which was or should be sharpened to ~5k, is going to degrade the edge.

        2. re: cowboyardee

          Alright folks, out of pure neurosis I just went ahead and got the knife sharpened through epic edge. The micro-chipping is gone, but as you can see, they had to remove what looks (to me) to be significant amount of steel from the edge:

          Part of it is that the lighting/contrast in the photos is different -- but there are definite differences. I guess my question now is if removing that steel will affect the capabilities of the knife? Does it degrade cutting ability to have an edge that is that "close" to the main steel of the blade? I don't know the terminology to refer to this correctly.

          1. re: jacobrb02

            It does seem like that they have removed a bit more than they need to. However, this is not uncommon as speed is essential for professional knife sharpener service. When you have a chance, it may not be a bad idea to learn knife sharpening on your own because you can really tune your knife the way you want to. It can be a fun little thing, but only if you have the interest.

            < I guess my question now is if removing that steel will affect the capabilities of the knife? Does it degrade cutting ability to have an edge that is that "close" to the main steel of the blade?>

            The short answer is: it depends.
            The longer answer is that significant removal of the knife edge can make the knife feels dull. It depends if the knife sharpener has taken the time and effort to address this. As you sharpen the knife edge more and the edge recedes, the area behind the edge becomes thicker. See this image:


            So while your knife edge has the same edge angle and is really just as sharpe at the very tip, you will feel the knife being duller because you need to apply more force to cut. This can be solved by thinning the area behind the edge (simple job) or thinning the entire blade (bigger job). See this image:


            My suggestion is that if the knife feels nearly just as sharp as before, then don't worry about it. You are fine. If you feel like the knife feels duller yet completely useable, then you can ask a knife sharpener to thin behind the edge next time you go for a full sharpening. Meanwhile, try to use the knife to see the microchip comes back. No need to worry about "thinning behind the edge" until you get a better handle of the "microchipping".

            1. re: jacobrb02

              They removed more metal than needed for a normal, no big chips sharpening sessions. Perhaps they found the OOTB edge over tempered / brittle (common with new knives), and opted to grind off the 'burnt' metal in one shot vs. several sessions.

              +1 on Chems' degradation answer.

          2. Congratulation on the nice knife.

            First, cowboy's comments are correct.

            Second, microchips although undesirable, are not unusual. A brand new knife is often simply prone to microchipping. Shun Classic knives are prone to this problem. A lot of people have observed microchipping in their brand new knives. After the first sharpening (removal of the microchips of course), their microchipping problem went away for good.

            Third, rock chopping does not have to cause microchipping. However, based on the photos, these microchips may be caused by rock chopping because they are concentrated in the front of your knife. What possibility happened is that twisting motion (lateral motion) caused them. Twisting motion (as well as moving the knife left and right; side to side motion of the blade) is never good for a knife, Western or Japanese, but more so for a hard steel Japanese knife.

            Fourth, I am not a big fan of honing. If you know how to hone, great. If not, honing can do more damage than help because you would be banging your knife against a ceramic surface. Needless to say, this can cause chipping.

            To answer your questions really quickly, the knife is safe to use, but I would try to fix the microchips whenever you have time. Either do it yourself or have someone grind them out. Give yourself a month or two to fix the chipping.

            After the knife is fixed, then I would try to do something for the next 2 weeks. (1) Try push cutting instead of rock chopping for 2 weeks and (2) try not to use the honing knife. A knife with this high quality does not need honing very often. Even if you want to hone it, I would not do it more than once a week.

            Hopefully, these two recommendations will alleviate your microchipping problem. If so, then you can try to add back your rock chopping after two weeks. If the problem comes back, then you know what causes it. If the problem does not come back, then you can keep using rock chopping.

            1 Reply
            1. re: Chemicalkinetics

              Thanks for your thoughts, I will try all that and get to the bottom of this!