Aikidoka
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Post by Aikidoka on Feb 15, 2015 17:13:18 GMT
I recently ordered a Masahiro Kill Bill Bride's sword from Kult of Athena. The sword had a slight bend near the tip, but was otherwise in great shape. So I decided to use this as a good excuse to make a pair of sword straightening tools: ![](https://lh3.googleusercontent.com/-jQLqo94bHTc/VODNSRNC6lI/AAAAAAAAAzw/23PgGBi36j4/w696-h522-no/20150214_115951.jpg) I bought an oak table leg from a nearby hardware store. I chose oak because I wanted the wood to be tougher than the wood used in a typical 2x4. I had to look through most of their oak table legs to find one that was made of one solid piece of oak, rather than 2 or 3 pieces glued together. I then used a hand saw to cut the 28" leg into two 14" pieces and then cut 1/4" slots about halfway through each piece. ![](https://lh4.googleusercontent.com/-Vs0QXqk7qGQ/VODMnD0iPTI/AAAAAAAAAzQ/OryZsiiQZ54/w696-h522-no/20150214_120050.jpg) The slots are 3/4" deep, which I would think should work well since, for all of my katanas, the shinogi-ji (blade flat) is less that 1/2" wide and that is where I want to apply the force to straighten and/or untwist the blade. I wouldn't think that you'd want to apply a large amount of force the ha (edge). ![](https://lh6.googleusercontent.com/-KdH2RukBuYc/VOELWv3KfGI/AAAAAAAAA0Y/i4wxK1S7ftA/w582-h165-no/parts_katana_blade.gif) When straightening the blade, I used a dry erase marker to draw lines on the back of the blade, which made identifying the location of the bend MUCH easier. The bend in this blade was actually a subtle kink, so I needed to first bend the blade in one direction, then move the tool slightly forward and then bend it the other direction. With these tools, very little force was needed to achieve a straight blade. After straightening the blade, I got out my belt sander and cleaned up the straightening tools a little, rounding the corners of the handles a bit, and then applied a tung oil finish. I didn't use sandpaper in the grooves, because that would leave behind abrasive residue that would scratch the blade. I smoothed out the inside of the grooves with a metal file. ![](https://lh5.googleusercontent.com/-FQtNsjwIJAY/VODSZHd1LPI/AAAAAAAAA0E/PJ-50Bgv3xQ/w696-h522-no/20150215_100328.jpg) It will be nicer to cut with my DH blades now, knowing that if I make a mistake, I can easily straighten the blade
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ShooterMike
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I like swords, and my snowman did too!
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Post by ShooterMike on Feb 15, 2015 18:17:43 GMT
Thank you, thank you, thank you!
The last 3 inches or so of my ATrim 32" Thorpe Falchion got bent and I couldn't figure out a guaranteed way to straighten it. Now I have it!
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Aikidoka
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Monstrous monk in training...
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Post by Aikidoka on Feb 15, 2015 18:36:14 GMT
Glad this helped, Mike.
The first time I tried the dry erase marker lines, I tried to look down the blade and guess where the bend was. Then I drew three lines in that area. I was WAY off! It's difficult to "eyeball" that sort of thing. Once I had the lines, it was easy.
One more thing: I always use the tools so that I am pulling them apart. That way, I can put them as close together as needed, which might be close for a sharp bend.
Good luck!
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Post by Lukas MG (chenessfan) on Feb 15, 2015 19:31:43 GMT
Thank you, thank you, thank you!
The last 3 inches or so of my ATrim 32" Thorpe Falchion got bent and I couldn't figure out a guaranteed way to straighten it. Now I have it! I wouldn't recommend this way on western style TH blades. It works well on DH blades due to their soft back but on TH blades it's not the best way. It works but all cold bending/forming stresses the steel more and is not ideal. I do it this way: You need: Soft wood/plastic brackets in a vice, small blow-torch, high grit sandpaper and a bowl of water (and the sword) GENTLY heat the area of the bend to straw yellow (about 180°C), pay special care to the edges, being thinner they can heat up real quick. Then quickly insert in vice (jaws slightly open so you can insert the blade easily, but close enough so you can precisely flex the blade at the right spot) and flex in opposite direction (it takes some experience and feel for the steel, usually one has to over-flex a bit, just straight isn't enough). Immediately take out, check and cool in water. If straight, sand of the color and reheat again to straw for stress release. If still bent, sand, reheat and repeat process. This process is a bit tricky and takes some courage because you're taking a heat source to the blade which CAN ruin the heat treat if you go too far. However, done properly it is the best way because it's the least stressful for the blade. Working under a bright light source helps when judging the colors.
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Aikidoka
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Post by Aikidoka on Feb 15, 2015 20:03:04 GMT
That's a good point. As I mentioned at the end of the article above, I built this straightening tool for my differentially hardened blades. If I had received a bent through-hardened blade, I would have returned it. But DH blades are designed so that they can withstand being bent and straightened many times.
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Post by RicWilly on Feb 15, 2015 20:12:40 GMT
On a related note, I saw this video recently. Notice the fellow on the blue platform straightening the swords.
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Aikidoka
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Monstrous monk in training...
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Post by Aikidoka on Feb 15, 2015 20:43:21 GMT
On a related note, I saw this video recently. Notice the fellow on the blue platform straightening the swords. Haha! I have seen that video before, but I never noticed the guy straightening the blades ![:D](//storage.forums.net/forum/images/smiley/grin.png) Yeah, I know people with years of experience are able to straighten blades over their knees, or in this case, he seems to be pressing it against the platform ( ![:-S](//storage.forums.net/forum/images/smiley/wavey.png) ). If he can do that, more power to him. But I wanted a tool that gave me more precise control. Another point, which I think I'll add to the original post, is that the groove is 3/4" deep. I would think that should be more than enough, because the shinogi-ji (blade flat) is less than 1/2" wide on all of my katanas. I wouldn't think that you'd want to apply a lot of force to the ha (edge), which is another reason that I probably wouldn't use the "platform press" method to straighten my katana...
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Post by RicWilly on Feb 15, 2015 21:14:39 GMT
Aikidoka, I like your straightening tools and think it a much better way than by hand. My point in posting the video was only to demonstrate that the bending and straightening of DH swords was not in the least unusual.
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Aikidoka
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Monstrous monk in training...
Posts: 1,452
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Post by Aikidoka on Feb 15, 2015 21:28:35 GMT
Aikidoka, I like your straightening tools and think it a much better way than by hand. My point in posting the video was only to demonstrate that the bending and straightening of DH swords was not in the least unusual. Thanks Rick! That's a great point to make. I remember when I first saw a diagram of a tool like this made from a 2x4 (on this forum, I think), there was a comment underneath it that said it would be okay to straighten a blade only 3 or 4 times in this way before the steel experienced fatigue. These katanas were originally designed to be durable in combat due to the fact that they would bend rather than break. A sword that would bend only 3-4 times before breaking would be only a little better than one that would break the first time. My understanding is that these blades can be straightened many, many times. I'll have to find some of the comments I have read in the past of dojo cutters that have been straightened hundreds of times and are still going strong. When I cut, I want to make as few mistakes as I can, but it is good to know that the sword can handle it when I do ![:))](//storage.forums.net/forum/images/smiley/cheesy.png)
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Post by RicWilly on Feb 15, 2015 23:14:05 GMT
On the subject of "metal fatigue". I had a Gen2 viking sword once that was fine when I got it, had decent flex and all to my inexperienced knowledge anyhow. Over time it got all bendy, as in it would bend and stay set tho I could bend it back very easily. It was as if the heat treat or whatever wore off. I figure it was defective. That is not to say that is what's going on with DH swords.
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Post by ineffableone on Feb 16, 2015 2:25:26 GMT
Aikidoka, I like your straightening tools and think it a much better way than by hand. My point in posting the video was only to demonstrate that the bending and straightening of DH swords was not in the least unusual. Yep that was the way I had always straightened my swords, like in the video. But I like the OPs simple little wood device. Seems like it would make it a lot easier to straighten a sword correctly.
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