Micro Bevel - KOBA

Even though I have a counter that tells me how many visitors I get to my Blog every day, I never know if that is just spammers or real people. Then I get a friendly email from a person who tells me reads my Blog. That makes this all worth it to me, even if one person is out there reading my sharpening journey journal, I will continue to add to it.

So this is for Jim.

I'm going to talk about micro bevels and what I know about them.  I've learned a lot from someone that I consider a top notch sharpener and just all around great guy, Jon Broida.

Ok... what is a micro bevel and what's it for and equally as important to discuss, do we need one on our knives?

This is an Alpaca, she wasn't interested in knife sharpening at all, she lives in Vermont.




Ok...

Basically, it is a very small (micro) area of the knife that is added to the primary edge,  so if you had a micro bevel on the knife, and laid it down on the cutting board as if you were cutting, the micro bevel is what is making contact with the wood, behind the micro bevel is the primary edge, the normal cutting edge and behind that is the secondary bevel. I hope this is clear, i.e. where the actual micro bevel is. Now in the picture above it is likely on a chisel so when I explain what a micro bevel is for that will make sense.

The Japanese term for a micro bevel is a Koba so from now on let's use that term, it is cooler and just easier to type :) 

What is a Koba for:

Well the picture on my nifty new T-Shirt says it all really.  The purpose of a Koba is to give extra life (longevity) to the edge of the knife or tool. So it is a common thing for a wood worker to apply a Koba to a chisel for example, those tools have a rough go of it compared to most kitchen knives so a Koba helps.

The way it is done is pretty simple, you sharpen the knife normally and let's say you put a 20 degree angle on the kitchen knife. (20 deg is pretty standard for softer knives). All you need to do then is to raise the angle to 23-35 deg and sharpen the knife with very light passes over your highest grit stone. So you're not re-sharpening, you're just applying a very very thin (micro) edge or bevel to the knife which will add strength to the edge. 

Is it necessary on your every day knife and for the home chef, I don't really think so, you could get yourself into a routine where you re-sharpen the knife once a week on that high grit stone or whatever stone you finish your knives on,  this is the best way to keep your knife sharp. 

In Japan, where they make those beautiful, everyone wants one, hand made knives like the  Yanagiba Deba, Usuba and regular chef knives the Koba is often applied as a final stage before it is sold  to not only increase durability of the edge but to clean off any debris left by the blade smith. I'm talking any burr, wire edge, it is how they make that edge perfect in not only sharpness but it's ability to retain the edge for a longer period.

Typically we add about 3 degrees to create the bevel but I learned from the gifted one Jon that the Japanese do this at a much higher angle, 30-45 degrees and one side of the knife only. 

So again, do we need one, a Koba?

If you work in a kitchen and spend 12 hours a day with your knife as many of the great folks I have me do, then you want that knife to stay sharp for the shift. A Koba should get you through the shift. Lets say you have taken your knife to a different level by sharpening it at a much more acute angle,  15 or even 12 degrees. Perhaps it is a hard enough steel to be able to easily handle that angle but again, under heavy use that beautifully sharpened knife, the primary edge is going to be tested. So a Koba will give some relief and get one through the day. 

A Koba doesn't effect sharpness either by the way,  it strengthens the edge without any penalty to sharpness. It is quick and easy to apply but I think you need to experiment with it to see if you are getting any extra life out of the edge,

A Deba, a traditional Japanese Knife designed for cutting fish, i.e. through the bones is a knife that would benefit from a Koba. The heel area especially is subject to a lot of abuse so the Koba will obviously help there.

What about my everyday knives, the ones I sharpen 75% of the time, do I put a Koba on the edge..no I don't .  Regardless of my efforts to keep a knife sharp for as long as I can, I don't know what the owner is cutting, or how he/she is caring for the knife. Also, I think if  I sharpen a typical Henckels or Grohmann knife at 20 degrees and the person isn't going to bring it back to me for 6-12 months, the Koba is not going to make much of a difference.

Now if a Chef gives me his/her beautiful Japanese knife and I know that every 3-4 weeks I sharpen it than I will apply a Koba. 

To summarize:  to apply the Koba just raise the angle at least 5 degrees and sharpen one side of the knife, you can do both sides but only one side is necessary. Use your highest grit stone and REMEMBER to make sure that the other side of the knife is cleared of any burr raised by the application of the Koba.

I just use a very very light trailing stroke on the same stone to remove any debris, it's very quick and just takes a couple of passes. 

To summarize the summary:

Another way to look at it in reference to the steel of the knife is if you have a softer knife, 54-58 for example, like a Henckels or Wusthof,  and believe me there is nothing wrong with that level of hardness. If you do have one of these, like most people do, including myself, then one would think that a Koba would be of great benefit since the edge won' t last as long on a softer steel as it would on a  60 plus knife.  To be clear, you can apply a Koba to any of your knives, it's a 2 minute process and as I said, doesn't impact the sharpness. 

I recommend trying it out, take 2 of your knives, knives of similar hardness and put the Koba on one and see which knife lasts longer.  You need to start with two sharp knives though to make it a feasible experiment.

Now when it comes time to resharpen the knife with a Koba, you just sharpen it normally then reapply the Koba, it is such a quick process.  (So you will grind away the very small Koba on the stones and then just put it on when you are finishing up with the 3k or 5k or even 2k stone). 

I hope you find this helpful, the key is to experiment with it, the Koba can be applied and removed very easily so if you don't like it, just take it off by sharpening at your primary edge angle. 

I just wanted you to see my new bread knife, this has nothing to do with Kobas :)

The coolest serrated knife I have every seen,