Strange warpage

How to restore antique arms & repair practice swords.

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Mark Duffner
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Strange warpage

Post by Mark Duffner » Sun Jul 25, 2010 8:29 pm

So yesterday I decided to graduate my jian from cutting water bottles to cutting aspen saplings. I walked out into my woods, and lopped up about half a dozen little trees up to an inch and a half in diameter. A couple of them seemed a little dry, but they still had green leaves on them. At the time it seemed like I could have done a better job with my machete, but that's not the point of this post.

You see, when I examined the blade after I was done the blade had developed a warp in it for the full length of the blade. How on earth could that happen? Can I fix it? The edge of the blade wasn't nicked or rolled over or anything like that.

Also, adding to my disgust, the handle, in both the side and edge axes, was slightly bent out of true. With an apparently weak tang do I even want to bother with this verdammte sword any more.

It is a Zhi sword from China. I spent about $300 on it, plus shipping, so I am a bit motivated to save the thing if I can. At minimum, even if I can't use it for aggressive cutting anymore, I'd like to restore it to true, if only for aesthetic reasons.

Thanks for any opinions or advice on this matter.

Mark

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KyleyHarris
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Re: Strange warpage

Post by KyleyHarris » Sun Jul 25, 2010 8:37 pm

Mark.

You probably would have been better with the machete for that task as they are more forgiving.

Long swords are designed with durability first due to the length and the stresses and force of impact they have to deal with.
The reason so many swordsman train so hard and so long on getting 100% correct edge alignment on their cuts is because its so easy to warp a sword blade. you could have spent $100 or $3000 on the sword and when something so long and thin passes through wood or bamboo at the wrong angle it flexes heavily and gets bent. Its easy to put the tip of the blade on the ground and show how springy and flexy it is and still return to true.. but if you put the sword in a Vice Grip and bend it where all the stress is focused on a single point then the sword will bend and set. This is what happens when you cut bamboo and wood and you are not 100% perfectly aligned.

You can bend it back with some small (or large effort). As to the handle coming loose. not a good thing. Is it able to be dissasembled? Some photos would be good.

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Re: Strange warpage

Post by Mark Duffner » Sun Jul 25, 2010 9:35 pm

Thanks for reminding me of a little fundamental matter, namely my edge alignment was probably off. I have to admit to this possibility and go back to the water bottles. However, I am still troubled by the handle being tweaked out of alignment with the blade. To disassemble the handle, I will have to drill out a rivet. Will have to reevaluate. This whole thing could just be me. :lol: :roll:

Thanks again.

Mark

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KyleyHarris
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Re: Strange warpage

Post by KyleyHarris » Sun Jul 25, 2010 9:38 pm

it probably should not have twisted the handle.. but there is a chance that when you edge alignment is off and your hand (holding the wood handle with a secure grip ) is going one vector and the blade is attempting to twist and go another vector, that the torque produced to bend the blade also twisted the tang inside the handle. it may not be a tight fit between the handle cavity and tang which would lead it to get the twist.

I wouldn't use it again for cutting until you verify that it wont get worse, and that you can correct it.

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Re: Strange warpage

Post by Nik » Mon Jul 26, 2010 10:42 am

I wouldn't put it like that "every" sword bends like that. Swords are bending like this under three circumstances:

1. They are poorly heat treated, resulting in having a too large soft core that has no spring capabilities, or entirely unhardened zones. This is an issue of quality control.

2. They have, by design and wanted, a soft core. This exists on makes that are worked for example after japanese originals that have such a design, historically, and for a reason then. This should not be the case with traditional sanmei constructions or monosteel constructions, as they don't have an iron core for shock dampening abilities. I know from experts that several samples of chinese made modern pattern-welded steel they tested contained an iron layer for the ease of make - this is unhardenable and will take sets on harder impact, as the steel layer on its own cannot develop enough structural strength. Such swords are practically designed to cut plastic bottles, and look good, for a budget price.

3. The impact is simply too large. I stress tested my own makes, and when applying enough lateral force to the flat side of the blade, it would take a huge bend. Meaning, I slammed it with full grown-man's force with the flat side onto an anvil, to see if it breaks (no-no) or sets (ok). So, when you hammer your blade in a bad angle into a harder, more resilient cutting target, the shear force will be too large and make it twist. However, this should not happen with small twigs. My own test swords of the last batch are tested by Thomas Holtmann, and he is regularly test cutting stronger twigs (not trees of course) without any problem and bending. The tang should not take a set at all, unless you are really overplaying it hammering grown trees with a lot of force. But that I would think takes a man with an incredible grip strength to manage that.


To me, this simply sounds like a quality issue. The blade was not correctly through-hardened and had a soft zone or core, unless you were hammering away on hardwood. I don't know what you actually call a "sapling", that can be anything from a finger-thick mini-tree to an arm-sized one that you couldn't chop with an axe in one strike.

BTW, you can easily repair that, at least optically. You need something like a 5-kilo smith's hammer, an anvil, and a person who has a good feeling for that. Then you simply look at the set source, and hammer it carefully with low-impact strikes (not strong, just enough) to ease out the set, the same you do when straightening a blade fresh from hardening and tempering. After that you need to repolish it as you would see the marks of the strikes.
Alternatively, you can heat up the blade a LITTLE, put it into a vise, and pull-out the set, but that also needs experience to not heat up too much, and find the right spot. After that, no cutting of harder, more resilient objects anymore, as repeated hammering or heating can weaken the blade to the point of creating mini-tears.

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Re: Strange warpage

Post by Mark Duffner » Mon Jul 26, 2010 10:38 pm

Much good advice and much food for thought. Thanks.

M

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Peter Dekker
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Re: Strange warpage

Post by Peter Dekker » Mon Sep 06, 2010 11:23 am

There are modern swords around that are less susceptible for taking a permanent set, but the way your Zhi sword bent is much like how an antique would look like after cutting with an improper alignment. I've got many antiques in with all kinds of twists and bends.

So although per today's standard we could see it as a quality issue, it may not have been an improperly made sword by the standards of old. But without examining the thing myself up-close an accurate judgement would be hard.

By all means, $300 may be a lot of money but it is not much for a cutting sword.

-Peter
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Peter Dekker
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Re: Strange warpage

Post by Peter Dekker » Mon Sep 06, 2010 11:26 am

By the way, here is an alternative method to repair twists by professional restorer Philip Tom:

viewtopic.php?f=13&t=433
Knowing is not enough, we must apply.
Willing is not enough, we must do.


-Bruce Lee

http://www.mandarinmansion.com
Antique Chinese Arms & Functional reproductions

http://www.manchuarchery.org
Fe Doro - Manchu Archery

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Re: Strange warpage

Post by Scott M. Rodell » Wed Sep 15, 2010 3:14 pm

There's good advice above about the twist likely being the result of low blade quality. I understand the desire not to just watch as $300 evaporates, but I suggest caution concerning the further use of this blade for cutting. Twists can be tricky to get out, but if you do & the blade is too soft, you will be weakening the blade further. What I suggest is a proper structural analysis test, I outline how to do this is my book. Simply put, put on appropriate safety gear, eye protection, etc, & cut into a solid wood target*, starting with light blows & slowly building up to full power cuts. Stop frequently to check the entire blade length for cracks. If you find crack, hang up the sword for good. If you don't, the blade should be good to use.

*out where you are, just find a dead pine tree, otherwise put a couple of 2 X 4's or a 4 X 4 in a vice & use that as your target.

Mark Duffner
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Re: Strange warpage

Post by Mark Duffner » Wed Sep 15, 2010 8:56 pm

Thanks for the advice. I was planning to do some cutting this weekend. I have some seasoned logs waiting to be cut into fire wood that will do the job for a blade test.

M

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