Here are some notes on various aspects of kitchen knives and knife repair that i have shared with customers recently. I hope many of you will find them useful.
Up First, a bit about sharpening single bevel knives, angles, geometry, and asymmetry-
An answer to a question posted on youtube... thought it might be helpful to some...
question: What angle will you recommend on the primary and secondary edge on a yanagiba?
answer: The exact angle will depend on the knife/maker/etc. However, these things can be quite easy to follow from initial sharpening. The angle doesnt change much between the two angles... its mostly pressure that changes. The main part is you know where you need to sharpen and you are trying to keep the distance from the shinogi line to the edge the same so as to maintain geometry. Hope this makes sense and helps.
question: Hello. Okay I will try to replicate the sharpening angle used before. It seems like it is about 11 deg at the primary edge.
answer: are you using a guided device for this? You may find that the angle changes a bit from heel to tip as well. This can make using a guided device a bit more tricky.
question: I do not use a guided device. Only freehand But I did not know that the angle is changing from heel to tip. Is it because it is impossible to keep a constant angle when freehanding or do the knife makers do it on purpose? Another question: On the sharpening video on the old channel you are sharpening a Aristugu A-Type Gyuto. What type of bevel do this knife have, single?, 30/70? Is this knife possible to buy?
answer: not all makers do it this way, but those that do have explained to me that the tip is thinner for more delicate work relative to the heel. On the A-Type sharpening, i actually dont recommend that kind of sharpening. It was just to show what i was doing to one of my knives at the time. That knife is still being sold at some places. The sides are asymmetrical, as well as the bevel. Probably somewhere close to 70/30, but numbers like this are over-simplifications.
in reality when talking about symmetry, people rarely use specific and exact angles. Likewise for the sides of the knives. These kinds of explanations are general over-simplifications japanese knife-retailers/wholesalers and sometimes makers use to help people who dont know japanese knives better understand one of the ways in which they are different. In fact, i just had this conversation with many of the makers no more than a few days ago.
Up next, a bit on machi gaps and Japanese Knives-
A quick note on machi gaps...
I know that many on here do not like them, so i thought i would take some time to explain a bit about them. First, the biggest thing to know is that there are regional differences in aesthetics. Kanto tends to like large gaps, while kansai does not. However, most knife makers/retailers/wholesalers in japan will still leave them if it makes more sense to than not. However, on request from many us retailers, many wholesalers in japan have started installing the handles flush with the handle. So, the question becomes "why leave a gap?"
There are a few reasons the gaps are left... here are some of the top ones
-When the neck of the knife is short (which can happen for a variety of reasons or sometimes none at all), the spacing between the choil and the handle becomes important. This space should be large enough to fit about 80% of your middle finger when holding the knife in a pinch grip. Smaller than this will be too small and is uncomfortable to hold. Larger than this will be too loose and can make rotary control of the knife more difficult than it should be. 80% or so gives enough space for the finger to fit, but is tight enough that the finger is still in contact with the handle for rotational stability. Also, what i have just said is based on what one would expect for a gyuto. Ideal sizes will be different based on knife types, expected grips, intended customers, etc.
-Handle installation... This is not only for ease of installing handles in the traditional japanese way (which is easier than using epoxy, allows for easier handle replacement, and removal of handles for maintenance), but also allows for knife placement relative to the handle. Knives with no machi will have a spine that is significantly lower than the top of the handle for example. On significantly harder woods (like ebony), the tang with the machi makes installation significantly easier with less chance of the wood cracking (which can be a problem with ebony).
Here are the top reasons i hear for people not wanting machi gaps...
-Food gets stuck. I've used knives with machi gaps for many years, both at home and in professional kitchens. This area is almost always covered with your hand and is not generally at risk for food getting stuck. If food does get in there, its a long way from being stuck, and comes out with general knife cleaning. If you find food accumulating, the chances are you may not be taking care of your knife well enough in my opinion. I've seen a wide number of knives from a wide number of people. I see just as many very dirty knives with no machi as i do dirty ones with a machi. I would venture to say, a dirty knife is more a function of the user than the knife design.
-It catches on your finger. I've found this to be the case with very large machi gaps or on some lower end knives that have machis that extend beyond the handle in width (or height depending on how you think about it). However, after significant testing, i've found that on knives with normal sized machi gaps, if this turns into a problem, it is most often the result of the use of an improper grip. When knives are held properly, your fingers dont really make contact with this area in a way than can catch.
-And of course, some people just dont like the way it looks... actually, this one is the reason i understand best.
The reason i say this, is that sometimes i ask makers to reduce or remove the machi gaps based on customer requests. However, i have a stipulation i have discussed with them. I would prefer that if and when they reduce the gap, they do it to an extent that does not sacrifice the ability to grip and use the knife well.
Anyways, hope this helps make sense of this to some of you.
A short while later, someone posted this in response to my above statement. I thought it was very interesting, so i'm quoting the post and response here:
Poster with Question:
I do not want to seem augmentative, so take these comments as the devils advocate if you please-
"When the neck of the knife is short (which can happen for a variety of reasons or sometimes none at all), the spacing between the choil and the handle becomes important. This space should be large enough to fit about 80% of your middle finger when holding the knife in a pinch grip. Smaller than this will be too small and is uncomfortable to hold. Larger than this will be too loose and can make rotary control of the knife more difficult than it should be. 80% or so gives enough space for the finger to fit, but is tight enough that the finger is still in contact with the handle for rotational stability.Also, what i have just said is based on what one would expect for a gyuto. Ideal sizes will be different based on knife types, expected grips, intended customers, etc."
This statement could be read as to be more about adapting the handle to a knife that was not made correctly. I have never seen this gap with any of our local knife makers here at the KKF. Is it a case of just get them out the door?
"Handle installation... This is not only for ease of installing handles in the traditional japanese way (which is easier than using epoxy, allows for easier handle replacement, and removal of handles for maintenance), but also allows for knife placement relative to the handle. Knives with no machi will have a spine that is significantly lower than the top of the handle for example. On significantly harder woods (like ebony), the tang with the machi makes installation significantly easier with less chance of the wood cracking (which can be a problem with ebony)."
Again, it seems like a case of expediency rather than quality here. Adjusting the installation to the tech rather than the end user seems back asswards.
Often times i have seen many US custom makers not think about this spacing, and only concern themselves with not leaving gaps. Some, however, do consider the spacing and adjust the neck of the knife to the size they need to install the handle. However, once the handle in installed, it can not be removed for maintenance (in most cases i have seen). Therefore, i could not repolish an entire blade perfectly... there would always be that little area near the handle that wouldnt be correct. Likewise for thinning a blade perfectly. This same area will be missed, therefore creating a high spot in that area. Its not often a problem in food release or cutting, but will change the look of the knife over time. By installing the handle with a little room for play, the handle can be removed when refinishing is necessary... same for thinning. On handles i've seen that use pins to keep the handle in place, the handles can be installed flush with the machi, but as the handle is removed and replaced overtime, the fit becomes looser. By being able to put it back on a tiny bit further each time, this problem is minimized with the japanese way of installing handles.
On the subject of handles, the choice of handles actually has great thought behind it, as well as the way it is installed. Here, we tend to have different ways of doing things, but in japan there are certain things a chef does that makes the need to replace his handles from time to time greater than what we see here. Ho wood was picked as a handle material due to its resistance to cracking in extreme climate environments or environmental changes. Other woods do not have this same strength. For example, ebony is one of the woods i see the most cracking problems with. It also happens on ichii and rosewood from time to time. Stabilized woods are not popular either, due to not being able to be installed the same way. The handles are installed in this way to allow for easier removal and replacement, as i previously mentioned. This is because most japanese chefs at higher end restaurants will sand down their handles a bit from time to time to keep them clean looking. This is very important to the way the think about their work environment, as well as the customer perspective in Japan. This means that handles wear significantly more quickly there. Being able to replace them easily is more of a necessity than anything else. And being able to do it inexpensively is a plus as well. Ho wood is also liked due to the lightness, which relates to the balance of the blade. When ebony handles are used, the end user understands that he/she will need to care for the wood significantly more so as to not have it crack. Likewise, it will change the balance of the knife significantly... especially on lighter knives (wa-gyutos, etc.). Traditionally, you see this most often on higher end single bevel knives, where the knives are forward balanced enough that the ebony handle doesnt change the balance in a really negative way.
Hope this makes sense in relation to your comments above.
Also, because many of the makers now know that americans dont like the look of machi gaps, the knives they make for export dont have them.
I think its also important to keep in mind we are buying knives that are designed with the japanese chef in mind (that's their history)... not the american chef. So often times the knives will adhere more to japanese chef's values than american, as in the case of handle replacement here.
And lastly, a note on checking for knife straightness-
Checking for Knife Straightness- A Quick Note
I recently have had a number of questions on and/or about this subject and i thought it might be nice to clarify a few things. Checking a knife for straightness can be very useful and is a very important part of knife sharpening. Here are a few notes on the subject-
-There are two knives of straightness one needs to be concerned with... warping from side to side and torsional twisting. Torsional twisting can sometimes be a problem and sometimes not (depends on the type of knife, grind type, and severity). Side to side twisting is almost always a problem (i say almost always because there may be a time when it is not... i just cant think of one off the top of my head).
-Checking for straightness is best done using your eyes, sighting down the blade in a variety of ways and from a variety of angles. However, it does take time to train your eyes to be able to see this well. Severe problems will be easy to see, but less severe problems can sometimes be very difficult to see. You will often sight down the blade spine from handle to tip and tip to handle, as well as the same with the edge side. It can also be a good idea to take a more straight on look down at the spine and edge. It can also help to look at the knife from the spine and edge, while holding it parallel to the ground with the tip facing to the right or left and the handle the opposite.
-It is not usually a good idea to test by laying the blade on something flat. This is for a few reasons. Most flat looking things are not flat. However, moreover, the grind on the sides of the knives will effect how this blade appears. For example, asymmetric knives may appear to be flat on one side while on the other the tip may appear to be bent upwards. This is an optical illusion and is a function of the grind and they way it lays on the flat surface.
-Slight warping on single bevel knives is sometimes seen. I had many discussions about this with very well respected professional chefs as well as knifemakers (sharpeners and blacksmiths). Server warping can be a problem in use and sharpening. Slight warping can be corrected through sharpening and does not need to be twisted back by hand (which i highly recommend not trying yourself... it is very difficult to do well and can potentially cause significant damage to the knife, not to mention you). Chefs and craftsmen agree that slight twisting does not effect performance in cutting and is best fixed by sharpening. More severe warping can be fixed by one of two ways... one will require refinishing the knife, but is the better solution. The other is more difficult and dangerous, doesnt provide as good of results, but can be done without refinishing the blade. I do not plan to share these on here, as when things like this have been shared in the past, many people attempt to do it and i end up seeing a lot of major problems that i need to fix. Sorry guys.
-Bending from left to right is often fixed with a tool used to bend the knife back. However, its not quite as simple as just picking the bent spot and bending it back. Like i mentioned above, when things like this have been shared in the past, many people attempt to do it and i end up seeing a lot of major problems that i need to fix. So i dont plan on explaining this in more detail to try to minimize this kind of problem. However, for those that have been to my shop, you can see me do this on a somewhat regular basis. This also requires great skill and experience to see well, and it has been my experience that fixing this kind of warping well also requires training and practice. I cant tell you how many knives i see for repair that people have tried to fix at home. Even when things seem to be fixed, there are often problems that the owner cant see. Anyways, this kind of repair is necessary to do before attempting sharpening. Sharpening a bent knife will cause issues with the bevel, profile, and geometry of the knife.
Again, i highly recommend not attempting this at home. Not only are the fixing processes potentially dangerous, but the chances of causing more damage than good are very high. I have spent a long time training in Japan to be able to do this well... not only in the actual repair process, but also in assessing the problems through visual inspection.
Hope this helps.
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