How to straighten out a D2 sword ?

[Valar God]

Greetings.

I have been making a katana for a year out of a stock of D2 steel,
by a stock removal method.

The stock was 1000 x 100 x 10 mm.

The katana is 7mm thick near tsuba and 4mm near the tip.

I have no special tools, not even a belt grinder.
I have only used a angle grinder and files.

I have been removing the steel only from one side of the stock
so that the other side would be the side I use as "zero point"
or the side that was supposed to be straight
so that I would be able to grind the other side to appropriate measures.

But during my work, the sword curved towards the side that was untouched.
Not at once but over time.
The more I removed the more it curved.

In picture, it would look like this:

The blue is the katana and the red is the removed steel from the stock.

The view is looking from the 1000 x 10 mm side.
Or looking at the back of the katana.

In my opinion, the reasons for this would be:

- From the heating of the grinding and cooling in the water,
some tension in the steel occurred, so the katana curved.

- There was a tension in the steel stock which appeared as a curve
after I removed the steel that was keeping the stock straight.

In the first case, I had suspected that the katana would straighten out
after the heat treatment, when the tension is releaved.

But it didn't.

So, I guess there was a tension in annealed steel which was not supposed to happen.

I guess that there are no more tensions in the steel
but that curve is driving me crazy.

So, the katana has been heat treated, 54 HRC.



I am asking for your help on how to straighten out my katana.



Would I do it by fixing the katana curved to the other side and leaving it
like this for a while,
or would I heat it while it is in that position ?

Or would I do it by hammering it cold ?

Or some other way ?


From the back:

From the cutting edge side:

It looks here like the curve is sudden but it is not, it is rather gradual.

Overall image of the katana:

Thank you.

 

[Hesparus]

Warping during stock reduction is a concern for all blades, especially long ones. Grinding, even with files, creates new stresses that cause bends. Getting it hot (warm, even) and running water on it will also bend it because it will cool differentially. These sorts of problems don't tend to fix themselves during heat treat, but may just get worse — as far as I know, you'll always want to get a blade as straight as possible before heat treat.
That said, warping during heat treat, even with an air-hardening steel, is common. There are a few ways to fix it.
1) Hammer it flat, as you mentioned. This is kind of dangerous because it creates so much stress in a localized area it can break, crack or chip the blade. It can also leave dings that are hard to get out. If you want to go this way, I'd recommend doing it on a soft surface (some people glue leather to the face of an anvil and hit it with a rawhide or wooden mallet, or you can glue leather to the face of a hammer).
2) You can clamp one end in a vice and bend it straight. This is a pretty good method, but it is terrifying and can be hard to control.
3) You can build a straightening jig for a vice. 2 methods: (1) use three short sections of brass rod, two go at the outside edges of one jaw of the vice, the other goes in the middle of the other jaw. put the blade in between the jaws and it will be bent by the offset brass rods as you close the jaws. The other method is the same in principle but uses wood. Wally Hayes has a set of replacement jaws for his vice that are made of hardwood and can be screwed into the vice in place of the metal ones. A lot of people like this method because it is easier to control than the others.
Whichever method you use, it will work better if the blade is hot. At least 3-400 degrees (f) makes the steel much easier to bend and less likely to crack when you do. Since you tempered it back to fairly soft, 3-400 degrees (f) shouldn't affect your temper.
You can try posting in the Shop Talk subforum for more information.
Great looking blade, though, and it's really impressive that you spent so much time on it. I'd love to see it when it's further along.

- Chris

p.s. I've never heard of D2 being used for a sword. Is it really suitable for that?

 

[Valar God]

I am thanking you from the bottom of my heart for your answer !

How will I make my Anduril sword then ???



About D2 for a sword.

I have been researching for a very long time for the best steel for a katana.

I wanted to do it out of W2, which should be the closest to traditional tamahagane,
but haven't been able to find it in my country.

In the end I decided for a D2.

Now, I wouldn't do it from any other steel except from DC53
which is, basically, advanced version of D2.

I have done many things in my life, metal, wood, electrics, mechanics ...
but I am new to bladesmithing.

This katana, a knife and a machete (special design) are my first work.
They have been heat treated recently and I'll make sure to post some pictures
when I finish them.

I wasn't 100% sure about D2, because a lot of talk about being not suitable
for a sword is circulating on the Internet.
But I kept working, with faith in it.

I have one person to thank to, for sharing his knowledge
by which I found out the hardness that I should put on longer D2 blades
and assuring me that D2 is a great steel for such purpose.

It is KyleyHarris, I see that he is active on this forum.
http://www.bladeforums.com/forums/member.php/234413-KyleyHarris

Take a look at his video (which is how I got that knowledge):
http://www.youtube.com/watch?v=fGU9aKE3A88

He has some great videos about D2 and about the blades that he makes.
I love his work and the way he is thinking.
It seams to me that people who like D2 think alike.


As for the knife and machete, although they are made out of D3 steel,
I had no trouble with them.
They were almost fully sharpened (unintentionally) before heat treatment
and the people there were worried about distortion
(I asked to quench them in the air too)
but there wasn't a single deformity on them.
Now I am sorry that I have left almost 1mm on the edge of the katana.

Here are a few more pictures of my work:


(click for larger)

(click for larger)

The profile of the blade:

Lenght: blade:73cm tang:24cm
Sori: 25mm
Blade geometry: saki sori
Weight: 890 grams

I think I am going with the vice method with heating to straighten it out.

I have made a mistake for not straightening it out before the heat treatment, right ?

Thank you again, I will try not to forget to post the results here.

 

[Hesparus]

You're welcome! I'm glad to help.
W2 is hard to find in any country. Any simple water-hardening steel should replicate the properties of a traditional sword reasonably well. To have a good hamon it will need to have as little manganese as possible (less than .3%). Anything from 1050, 1060, 1075, up to W2 will give you a pretty traditional sword. Wally Hayes makes some great katana out of 1050, for example. The real attraction to W2 is that it produces the most dramatic hamon because of the high carbon and the vanadium (I'm told). The simple carbon steels should be widely available in pretty much any part of the world (certainly if you can get D2).
Normally I'd recommend Wally Hayes' DVD on making semi-traditional, stock reduction katana, but it seems like you've got everything under control. You would probably still learn a lot from it, though.
And yes, you will want to straighten before heat treat. If you work both sides equally, you can minimize the differential stresses on your blade such that it will warp less.
Thanks for sharing the new pics, that's a great looking sword! I'll be interested to see how it gets mounted.

- Chris

 

[Valar God]

Thank you again.

I took a look at Wally Hayes's work and it is very interesting.
I'll check it out more thoroughly. Thanks.

For the fittings, I'll make them myself and I expect them to be
very pretty and somewhat extraordinary.
I hope it will be soon enough.

Somehow, I have missed to post a few pictures which show the katana more detailed.
I copy/pasted the links but it is missing.

What I have done that is not "by the rules"
is that I have made an integrated habaki.
I don't have tools for bending or welding of the copper
and this way makes more stronger connection between the blade and the tang
and less dirt finds it's way under habaki.
It is more how I had to do then how I wanted for some reason, but I like it.

Point of balance:

Cheers.

 

[Valar God]

I have made an attachment for my vice today:

I have put some leather over the metal
but it looked ugly so I didn't take any pictures.

I have tried.... and failed.

Not that I have ruined the katana, I just didn't manage to straighten it.

Obviously, my vise is too weak, apart from the bad "handle".

I think I will give up for now.
I was afraid even before.
To straighten it, I have to pass the elastic deformation of the metal
and I am scared about the consequences.

I have managed to bend it to a certain extent but it came back.

What I have gained from this is a conclusion that D2 is an excellent sword steel.

I see that there is a Kevin Jones active on this forum.
I don't know if it is the same Kevin Jones from UK that has written an article
about D2 katana few years back upon which I made my final decision
to make my katana out of D2.
I like to get credits for my contribution
and therefore I try not to miss crediting the people who have helped my
so I will use this chance to thank Kevin Jones for that article.


I will sharpen, polish and make a tsuka with fittings.
Then I will see how it cuts and performs.

After that I will decide if I am gonna try again
so that I don't have to make a curved saya.

@Hesparus, thank you very much

but I don't have the tools at this moment to do this right
and honestly, I don't have the courage.

If I don't succeed, I will consider this as a beginners mistake.

I hope that I will have the will to make another katana.

I have a knife and a machete to finish now
and I will let the katana "sleep over" for a while.

Cheers.

 

[Hesparus]

I find that straightening blades, especially when I've spent a lot of time on them, is very scary. Every time I do it, I worry that the blade will snap in half at any second. But if you go slowly and work with your blade hot then you should be fine. Sometimes it's best to wait a little while until you work up the nerve. So good luck to you for whenever you decide to pick this one up again.

- Chris

 

[Valar God]

Thank you very much, your words are inspiring indeed.

I will try again then, soon enough.

 

[Valar God]

I have thanked Hesparus privately for his kind help,
but I was still restless because I haven't done it publicly.

Few weeks back I have prepared the tools again, this time a bit better.
I had to take a stronger lever for my vice, the original was to weak
and I welded together the two bending "tools" that are on the same side of the vice
in order to keep them at maximum distance from each other
because, that way, I need less force and it makes less risk of breaking or making some mistake.

Pictures again because the ones from before are not there anymore:

I heated the blade, like the last time, so that I can't hold it in my hand,
put in vice and bent.

I can't say, looking back, what was the angle needed to bend the sword in order to become straight
but I can say that it needed more than 20 degrees.
Or that was how much It was in my case.
Perhaps even around 30 degrees, I can't say because my heart was pounding like I was robbing a bank
and the last thought on my mind was measuring the angle.

The steel took it more than well.
D2 is said to be fragile but that was not my experience from this case.

What was needed is to bent it multiple times, like every few centimeters,
in order to get "homogeneous" straightening.
Because I had a homogeneous curve.

There wasn't any "over-bending" while banding it back.
I have bent it practically as much as I could (with my equipment),
or as much as I dared to,
and that was just enough.

I was afraid to do it, but in the end it wasn't that scary.
I am not saying that it would be easy for me to do it again if I had to.

Hesparus, thank you very much.

Perhaps this info will also be useful to someone with the same problem.

Cheers.

 

[Hesparus]

Way to go! I'm glad this worked out for you. If you ever do this again, I'd keep a close eye on how much you're heating the blade. "Too hot to touch" can be a huge range, from ~150ºf on up. The hotter you make it, the easier it will be to bend, but you want to make sure you're not getting it so hot that it will ruin the temper. 300-400ºf should be good, but check the tempering charts for you steel.
I'd love to see more pics as you mount it.

- Chris

 

[gregorio]

that vice setup looks nice, glad it worked

 

[Valar God]

Thanks.

I could use a larger one, but it was good enough, luckily.

 

[BePrepared]

I would really like to see that blade once you have it completed. That's a SWEET looking geometry.

My favorite knife is made of D2. I wonder how a katana or waki made of it would hold up

 

[Valar God]

Thank you.

I am working on it. I hope that I will finish soon.