Tanto Advice

[Alex Melton]

Hello,

Recently, I have been trying to make my own tanto-style knife in the traditional form. Yesterday, I cut out the basic shape of the blade from 12" 1095 steel that is 1/4" thick. Then I refined the blank using an angle grinder and a 12" bastard file. Next, I marked my center line on the edge of the blank and proceeded to my rookie 4"x36" belt grinder. I started by grinding down to just above the thickness of the edge I want and then pulling that grind angle back until the bevel would touch the spine. At least, that was my plan when I ran out of grinder belts. Not wanting to give up, I headed over to my workbench and began to work with the 12" file. Man that is tiring work!

Today, I finished (or at least I think) filing the bevels down to almost proper hira zukuri geometry. I also filed the spine of the blade to the pointed geometry it has.

Some questions still remain though. How do I make sure that the convex geometry (the niku I think it's called) I filed is the same on both sides? Also, do you have any tips for the heat treat? I plan on doing a hamon (my first :D) and quenching the steel in some warm/hot canola oil.

I know you experts might cringe at my rookie work, but I strongly support any criticism. If this turns out to be a failure it will most certainly be a learning experience.

Thanks! 

[ScottWright]

I'm not expert on Japanese knives but for evenness, I started out using layout fluid (blue) and my calipers to help mark and measure all my file work and grinding. I still it find it extremely helpful after my first year. It gives you a clear look at what you are and aren't getting.

[Wes Detrick]

I would say that the tip is too blunt.  It is a pretty dramatic up sweep from the edge.  Do a google search for Japanese tanto, and look at the provided examples.  The hirazukuri style has a much more graceful and tapered approach to the tip.   Typically blunter types are characteristic of the smishsmortions people call American tantos.

As far as checking your appleseed shape,  you should be able to feel it.  Pinch the knife inbetween your thumb and forefinger and run them from the spine to the edge.  If an area feels fatter one one side, mark it.  Do this down the length of the knife.  It is not the most precise, but your fingers are better than eyes lots of times.  

As far as the hamon goes, get your oil hot, like 120 degrees hot.  Your clay coat does not need to be thick, maybe 1/16th of an inch.  If you are going to put a wash on the entire blade, make sure that it is SUPER thin, and dry before you apply the clay on the spine.  The hotter the blade gets above the critical temperature for your steel, the less active the hamon will be. 

 

[jake cleland]

yup, the tip is definitely too short and blunt - for a hira zukuri blade the tip length should be about 1 1/2 x its width. You might also want a bit more taper in width from the machi to the start of the tip. To get any kind of depth of hardening in oil on 1/4" 1095, you'll want to take the edge down to about 1.5mm, and leave off the clay wash on the exposed steel - it just slows things down in oil. Remember that any sori will be negative in oil. You can mitigate this by hardening portions of the spine.

[Alex Melton]

Thanks, guys!

I've filed down the tip so that it has a much more gentle curve to it. The edge thickness has been refined also.

Since the tanto is pretty short and thick, I don't think that there will be much of a curvature--but are you saying that the curvature would be toward the blade side? I thought it would only curve toward the spine as long as the clay is along that side...

[Alan Longmire]

In oil it will curve toward the blade edge.  That's just physics.  The degree of curvature depends on blade geometry and oil speed.  Faster oil usually gives less curvature.  A really fast oil like Parks 50 is best.  Hot (~130 degrees F) canola is much faster than room temperature canola, but not nearly fast enough to avoid some nosedive.  Using 1095 and hira zukuri geometry you shouldn't get a lot of curve in hot canola, but it will happen to some extent.  It would be a bit less with shinogi zukuri just because of the added mass.

[Alex Melton]

Alright, here it is! The tip is still a bit blunt but much less so than it was before. I think it will do fine.

I proceeded to use 120 grit sandpaper backed by a strip of some 440C I had lying around and removed all of the file marks on the blade. I also refined the tang shape.

Tell me what you think! Right now the clay for the hamon is drying. Hopefully, I will be able to quench and temper tonight.

[J Broddrick]

Hi Alex,

to my eye it's still a little "boxy" but if you are happy then run with it!

where is the 1095 from? Since you did stock removal you might need to thermal cycle the blade a few times before quenching. If the steel was spheroidized annealed it won't want to harden unless you soak it at a reasonably high temp to free up the carbon. I had this problem in the past.

Last suggestion, watch the clay thickness at the machi. It's the thickest part and the nakago holds a lot of heat. It's really easy, especially in oil, for the hamon to run off the edge of the blade before the machi due to this fact.

good luck!

[Alex Melton]

You're right, it is a bit boxy to my eyes too. If/When I make another one, I am certainly going to make it more slender and longer.

I've had the 1095 for a while, so I don't know or remember where it came from. However, I do know that it is 1095 because I labeled the billet.

Because I wasn't sure if the steel had already been annealed, before I started grinding I placed it into my forge to anneal. I raised it to about orange heat and turned off the forge and covered the openings with bricks so it would slow cool. (My forge construction keeps heat for a long while after it's off and I didn't have any hot sand on hand to shove the blade into.)

I don't know if my one attempt to soften the steel worked well enough to allow it to quench, but we will soon see.

Thanks for the advice on the hamon! I will be extra careful with the machi.

[SteveShimanek]

You have a lot of extra steel in the tang (nakago) that will make the knife unnecessarily heavy and create issues when you put your handle on. Blade proportions look much better. Good luck.