Straightening a Bent Sword Blade

How to restore antique arms & repair practice swords.

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Scott M. Rodell
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Straightening a Bent Sword Blade

Post by Scott M. Rodell » Wed Jun 21, 2006 2:02 pm

One downside of practicing test cutting is that sooner or later you will damage the sword you are training with. Recently I was testing the limits of several swords on dry 2" thick bamboo wrapped in a single rice straw (tatami) mat. In the course of testing one sword was bent. Bending a blade is preferable to breaking the blade or chipping or cracking the edge. Overall, the fact that the blade bent instead of breaking while sustaining no edge damage, demonstrated that the blade was well made. However, it did leave me with an unserviceable sword. Naturally it wasn't long before I was on the phone with my good friend, & sword smith, Paul Champaign. He provided me with a simple method for straightening the blade which I outline below.



Before reading the instructions below the reader should understand that he or she is proceeding at their own risk. Neither the author or GRTC take any responsibility for injury or possible damage to the sword you are working on if you attempt to use the method described below to straighten a bent sword blade. The reader should also take care to first check the blade for other damage before attempting to straighten it. If the edge is also chipped, this chip must be polished out before attempting to straighten the blade. If the edge is cracked, or the blade is cracked any where at all, do not attempt to straight it or use it for cutting again.



Always wear safety googles & remember the blade you are working on is quite sharp so there is a very real possibility that you will cut yourself, perhaps seriously. It is wise to purchase a kevlar glove for performing this task & other repair or restoration jobs



These tools plus a pair of safety googles are what you will need to straighten sword blade that has been bent during test cutting practice.



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Blade Straightening, Step 1-

Post by Scott M. Rodell » Wed Jun 21, 2006 2:03 pm

Step 1: Keeping in mind that the blade is very sharp & can cut you, sight down the blade & use masking tape to tape along the flat of the blade opposite the bulge of the bend. Then mark the point of the apex of the bend. Most bends are not continuous curves.



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Blade Straightening, Step 2-

Post by Scott M. Rodell » Wed Jun 21, 2006 2:04 pm

Step 2: Rest the bent blade on two wood blocks of equal thickness with the marked apex of the bend over the center of the space between the two wood blocks.



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Blade Straightening, Step 3-

Post by Scott M. Rodell » Wed Jun 21, 2006 2:05 pm

Step 3: Secure the blade, & the wood blocks it is resting on, to your workbench so that they do not move when setting up the "C" clamp during Step 4.



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Blade Straightening, Step 4-

Post by Scott M. Rodell » Wed Jun 21, 2006 2:08 pm

Step 4: Attach a large "C" clamp between the two block so that it presses directly down on the apex of the bend as marked in step 1. Apply enough pressure with this "C" clamp to secure the blade so that it will not slip & then remove the other clamps. Then continue applying pressure on the apex of the bend with the "C" clamp until the blade is straight.



Leave the blade in this position for 10 to 20 minute then remove it & check if it has been straighten. If it has not straightened, repeat steps 2 thru 4, only increase the pressure with the "C" clamp past straight. Repeat as necessary until the blade is straight.



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The blade that was being straightened in the demonstration photos required several repeated treatments where the clamp was left in place bending the blade past straight in the opposite direction of the bend for 20 minutes each treatment. Blades made of modern steel will require more pressure to straighten then those forged of tradtional steels.
Last edited by Scott M. Rodell on Fri Dec 14, 2007 7:11 am, edited 1 time in total.

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Post by Philip Tom » Fri Dec 08, 2006 2:51 am

You will find also that differentially heat treated blades (those hardened in the area of the cutting edge(s) only, and softer at the spine or ridge, tend to be easier to straighten than those tempered to the same hardness all the way through. I once straightened a World War II Japanese officer's katana with relative ease despite the fact that the bend was at the thickest portion of the blade, and have had a literal nightmare trying to remove bends and kinks from spring-tempered European blades.



The method explained in the above post is an excellent one. All I'd like to add is that if you are especially concerned about preserving your blade's finish, you might want to put a piece of leather or stiff cardboard between the blade and the face of the clamp. Many C clamps have rather rough edges that might press through the layer of masking tape to mar the surface of the blade.
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Re: Straightening a Bent Sword Blade

Post by Scott M. Rodell » Thu Aug 21, 2008 12:16 am

Scott M. Rodell wrote:One downside of practicing test cutting is that sooner or later you will damage the sword you are training with...
Last week, out in Bozeman, we were practicing Test Cutting the evening before the regular Chinese Swordsmanship seminar & saw just how easy it can be to bend even a good sword if there is a problem with one's technique. We were cutting single rice straw mats when one of students bent his classmates jian about 5 degrees off straight about a third of the way down the blade. This bend resulted because he didn't maintain the proper edge angle, rotating the blade out of parallel with the plane of the cut, when contacting the target. It was as if he had hit a small tree with the flat of the blade. Fortunately I was able to straight it right out again & the student whose sword it was took it as a lesson in how to straighten blades.

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