Introduction: Making a Knife With a Japanese Hamon

Picture of Making a Knife With a Japanese Hamon

Have you ever noticed the wavy line on Japanese swords that is shown in just about every single anime and samurai movie? The proper name for this line is a Hamon and if you want a sword with a real one adorning its edge that will set you back a few grand. However with patience and decent understanding of metallurgy its possible to create a blade with a Hamon on it.

Disclaimer: This instructable just shows my process, if you decide to make your own I hold no responsibility for any errors or injuries that you may make. Knife making is dangerous and should be undertaken with extreme caution.

A few materials and tools that I used are as follows;


1) A simple clean high carbon steel with a low manganese content: I used 1095 for mine, but W1 or W2 work fine as well.

2) Some sort of knife handle material: there are far too many to list but I went with walnut.

3) Pin stock: again there are many options for this and I used brass.

4) Various grits of sandpaper: I used every grit from 80 to 3000 but it really depends on what look I am going for.

5) Some method of shaping steel: In this tutorial I am not really going to be covering how to shape the blade and instead will be looking more at the metallurgy. However angle grinders and metal bandsaws work great. But since I felt like being cool I forged mine out.

6) Acid: I am using PCB solution, which is normally used with etching circuit boards. The active ingredient is Ferric Chloride which is what we are really after. Since I am using acid I made sure to have some way of neutralizing the acid and safely storing it

7) A water based refractory cement: I used "satanite" but i have seen people use wood ash and charcoal and other ingredients.

8) A method of holding a constant temperature of around 1500f (815c): while this is a crucial step just be aware that reaching high temps like that can be very dangerous and I made sure to have a fire extinguisher on hand at all times.

9) A proper quenchent: water can be used but it will most likely break the blade. Instead I use "parks 50" quenchent

10) Epoxy

11) Most importantly safety gear should be worn at all times! I cannot emphasize how important this is, I use a good pair of leather work gloves, a good pair acid resistant goggles and gloves, long sleeve non-synthetic jacket or shirt, and the best respirator I could buy.

I am sure there is more stuff I could include but that covers all of the basics.

Step 1: Rough Shaping

Picture of Rough Shaping

To start this bad boy off, I took my piece of steel and forged it to the initial shape I wanted, making sure to thermal cycle the blade when I was done.

To thermal cycle the steel I bring the blade to above its critical temperature in the forge and let it air cool to room temp. I then bring the blade back up to just on critical temp and back down to room, and finally one more time at just beneath critical temp and back to room. This process relaxes the steel and re-aligns the grain structure.

Critical temperature of the steel can be found with a quick Google search. 1095's is approximately at 1350F.

Step 2: Further Rough Shaping

Picture of Further Rough Shaping

Using a belt sander and set of files, I went around and cleaned up the the profile of the blade and flattened the bevels making sure to leave about a dimes width at the thinnest section. This thickness prevents the bade from warping while it experiences the thermal shock of being quenched.

Step 3: Preping Your Hamon

Picture of Preping Your Hamon

Alright, finally the blade is all cleaned up and looking, oh so fine. Now, I make sure to first coat the entire blade with a thin layer of refractory cement. This will ease the stress that the quench will be placing on the blade. After the first layer drys, I add a second layer somewhere between 1/8" thick and 1/4" thick all over the blade and handle, leaving about 1/4" behind the edge bare .

Step 4: Heat Treatment

Picture of Heat Treatment

This is the most nerve wrecking, as well as the most fun part of knife making in my opinion. What made this part really special for me was that it was done in the bathroom of my apartment, which I highly recommend nobody doing ever!

Anyway, lets learn some metallurgy! To start, it will help to know that steel has a crystalline structure and when it's superheated and then cooled this structure does some neat stuff depending on how fast or slow it was cooled. When we bring this blade past its critical temperature of 1350F and up to its final temperature of 1475F all of the grains become super soft and easily manipulated.

Putting this in perspective, you could heat up a bar of steel to critical and drop a cup on it. That small impact would actually deform the steel pretty significantly. However if you were to take that same piece of steel at room temp and drop the same cup from the same height, the steel would jump up and karate chop the cup, breaking it into thousands of tiny little pieces...seriously.

Depending on how fast the steel cools you can change its grain structure to make it function better at different things. Which is the why the clay is used in this process. The thick coating on the spine cools the steel slowly turning the majority of the structure into the strong and resilient ferrite and cementite, known for their ability to take a beating. However the thin coating along the edge will loose heat extremely fast which creates Martensite a structure much harder than Ferrite and thus will stay sharp much longer. I want you to guess what the border between these two states is, yep, you guessed it, that's the Hamon!

Now this is the last super sciency bit. Immediately after quenching, the blade become super hard all over, dropping it at this point will make the blade to shatter like glass and cause my face to look all weird, scrunched up and covered in tears. To avoid this we place the blade in the oven at around 400F, allowing the steel to soften enough to become usable, but not soft enough to lose its edge-holding ability.

Step 5: Cleaning the Flats

Picture of Cleaning the Flats

Phew, there was a lot of writing in that last section, this one is pretty quick to type but takes forever to actually do.

Sand it so the blade until looks pretty again with increasingly fine sandpaper.

Told ya that would be fast.


PROTIP: If you want a really nice hand finish on anything metal sand in straight lines and and every time you increase the grit, switch the angle that you sand at. This allows you to see all the scratches from the previous grit, once they are all gone, increase your grit.

Step 6: Acid Etching

Picture of Acid Etching

Now that the blade is pretty again, lets play with acid!
I First dip the blade into the acid.
Then into a neutralizing bath.
Then into a tub of regular water.
Let it dry.
Sand it with the finest grit I have.
Repeat all those steps until the etch is visible enough.

Step 7: Finishing the Handle

Picture of Finishing the Handle

After the etch is done, I cut and shape the walnut handle scales and attach them to the blade with epoxy and brass pins.

I then wet the handle slightly and sand off any of the fibers that stick up. Afterwords I progressively sand with higher grits until its nice and silky smooth. I finished this knife off with some Tung oil, which gave it a richer color, and aids in water resistance.

Finally I sharpen the edge on a whetstone, which I may make a tutorial on at some point in the future.


Anyway I hope you learned a little something, If you have any questions don't hesitate to ask!

Step 8: DONE

Picture of DONE

This whole process can take about 20-30 hours with most of it spent on doing hand sanding. Very fun and very rewarding, as long as you are safe about it.

Comments

ConnerM6 (author)2017-01-08

Dude if you're adding a hamon you don't heat treat it in a traditional manner. The hamon line is essentially heat treating it. The areas where the cement is added the blade doesn't get as hot, so it stays softer, whereas the hotter edge becomes fully hardened during the quench. Also, when making a traditional Japanese sword or knife, the quench would be done in water, it helps bring out the hamon.

clockworkfish (author)ConnerM62017-07-06

Water or brine are awesome for doing Hamons yes, however, since the water will immediately turn to steam on contact with the hot steel, a vapor jacket around the steel which increases the likelihood of cracking and fracturing. Instead, using a oil like Canola oil, or a commercial quenchent like parks 50 (used in this tutorial) allow you to cool parts at almost exactly the same speed as water without forming a vapor jacket. In the end oil gives you very low risk but nearly identical results.

GrimmBuilds (author)2017-05-07

Hi, just thought I'd make a small correction, you are in fact making ferrite+cementite, also known as coarse pearlite (at a temperature just below the eutectoid temperature) not just ferrite. Thanks for the post.

Awesome thank you a bunch for fact checking!

RileyL12 (author)2017-06-30

What was the neutralizing bath you used? Ive made a hamon on my katana and im ready for the acid etching, I just need to know what to use for a neutralizing batg

clockworkfish (author)RileyL122017-07-06

I just mixed baking soda with water, you could also add a bit of windex (contains amonia) to the water. Though I'm unsure of what the ratio was :/

Jim L. made it! (author)2017-06-15

Well done! I use bentonite clay (ground and hydrated {clean} clay kitty litter) to do my differential heat treat.
I sand to 600 grit then apply the clay in a (hopefully) pleasing pattern to the spine and both upper bevels; heat to nonmagnetic and quench in used fryer oil.

Heat treat is completed at 400° for 1 hour in the oven. I am still living and only allowed to do this because all traces of oil have been vigorously cleaned from the blade prior to placing in the wife's oven.

clockworkfish (author)Jim L.2017-07-06

Oh man awesome work! tossing them into a baking tin works great to avoid oil getting everywhere, plus makes it super easy to transfer! Also nice skeletonizing! Keep it up! :D

ZiggyBaggins (author)2016-10-01

Where did you get that thermometer when you were heat treating the blade?

dpittman5 (author)2015-02-28

whats?

lordna (author)2014-05-09

Looks awesome. One question, in the heat treatment section it doesn't mention specifically if you are quenching with the refracting cement on the blade or not. I'm assuming so, but doesn't it fracture the cement.

clockworkfish (author)lordna2014-05-09

Yupp! And the cement may have some light fractures, nothing that will impact the outcome from what I can tell.

hzxasdf (author)2014-03-02

很好。。。。。,,

Lextone (author)2014-03-01

Thermo cycling the blade is one of the most overlooked steps in knife making. I made knives as a hobby several years back and picked that tip up from an old time blacksmith. It really does make a difference in the finished product. Another tip he gave me was to anneal in ashes, harden in oil and temper in water. Always worked for me.

Beautiful work.

xd12c (author)2014-02-28

looks beautifully done. How did you heat it up in the bathroom?

clockworkfish (author)xd12c2014-02-28

I have a small kiln that can run up to 2000F and unlike most kilns it can plug into a standard 120v outlet. It is also portable enough to fit under the sink of the bathroom in that apartment. Conveniently the sink was just held up by a couple metal poles and had no wooden cabinetry to get in the way of any red hot blades. I have since moved out and no damages were made except a few places where the acid ate my bathtub, which was not taken out of my damage deposit...score!

xd12c (author)clockworkfish2014-03-01

do you have a brand name or anything like that? I'm looking for something exactly like it.

clockworkfish (author)xd12c2014-03-01

I use a Skutt Firebox 8 with a k-type thermocouple and I do not have the PID controller. If you are looking to buy one I highly recommend the PID, since the name of the game when it comes to heating things is control. Without it I can stay 15F +/- but that's after practice, and with one you can stay within 1F+/-, and if that doesn't convince you enough already, without a PID you have got to sit by it at all times, while with one you could walk away and do other things.

TL;DR Skutt firebox 8 with PID controller is what I would get if you want a small kiln

Ironwave (author)2014-03-01

This is completely awesometacular.
Good job.
Step 5
Protip
Last word - increase your grit.
Should it not be Decrease your grit?

clockworkfish (author)Ironwave2014-03-01

Hmm, not sure? If you think about it that statement could go either way, I meant it through the idea that increasing the number gets a finer grit.

Ironwave (author)clockworkfish2014-03-01

Got it.

jmwells (author)2014-02-28

Good looking. Ok next level, Damascus steel, that's when it really gets tough, and really beautiful.

clockworkfish (author)jmwells2014-02-28

I have been wanting to learn how to do Damascus for a long time! When I have access to a decent shop with a forge and everything that will be one of the first things I play around with!

jmwells (author)clockworkfish2014-03-01

I started very small. A three inch blade folder. My largest so far is six inches. I started with pieces of auto leaf spring. I quench with used motor oil that is circulated thru a homemade heat exchanger. I use a homemade hammer mill. It ain't pretty, but I'm having fun with it. Learning a lot.

clockworkfish (author)jmwells2014-03-01

Try working with some 5160, its cheap, plentiful, and makes for an incredible knife if you treat it with respect. Also try quenching with a commercial quenchent or canola oil. The reason I suggest all this is because then you can start working with known variables, and because old motor oil is filled with a lot of stuff you don't want to inhale via quenching smoke.

Regardless thats awesome! Keep it up man!

tclemmo (author)2014-02-28

Wow, that is a beautiful knife! I can see you have put a lot of time and effort into it. Great job!

chewy21 (author)2014-02-28

nice job !

shantinath1000 (author)2014-02-28

nice work!

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