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I Forge Iron

W1 sword second failure


Steve Shimanek

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My second katana project just turned into a wakazashi and possible kaiken....I am having a lot of issues with bends and have broken them trying to straighten. Grain looks ok, i have been normalizing 3 times after forging and cleanup. I have not tried to straighten after tempering; i have just heated the area and attempted straightening by gentle hammering and/or hand pressure. Any ideas how i can avoid these problems? Steel is new W1 from Enco forged down from 1 1/2 round. Thanks, Steve

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First try to determine what caused the sword to warp in the first place, correct that problem and you won't have to worry about straightening them. One of the biggest causes of warpage in knives and swords, I broke two swords before I got it right, is uneven grinding, that is the blade is ground flat on one side and rounded on the other side. The rounded side having more metal quenches slower than the flat side and the blade warps toward the flat side. Take a look at the broken ends and see if the grind is the same. If you have a blade that warps in heat treating, normalize the blade, then heat and straighten, normalize and then heat and quench, if the blade warps the same way the second time it is usually a problem in the grinding of the blade.

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Can't comment on W-1, but with my long 5160/spring steel blades, I quench for a count of thirty, then have another thrity seconds or so to flex warps back straight before the steel sets up all the way.

A *very* useful trick for straightening at the point of tempering is to temper it once, then lay a flat, thick-ish bar of steel (I use an old file) along the blade with the flat along the inside of the curve. Then you C-clamp the warp against the file and cycle it through again. It's often useful to put a couple of washers between the file and the blade to let you flex it over a little more. It may take a time or two of tempering with it clamped, but it'll pull the warp out.

This trick was something I learned from Rick Marchand and has been very helpful.

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I always use sword tempers to straighten and the meta stable austenite stage as well normally by hand with a vice and gert big pair of scrolling tongs flexing past the warp. . I is my experience that sword blades warp and therefore need straightening

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This blade was water quenched and was done w/o clay as an experiment. The grain size could have been a little smaller but I don't think that was the main problem. I had it in the vice when it broke; it appears from the visible structure that it through hardened which would make the blade more likely to snap when trying to flex out the bend. The grinds were very even; I am thinking that maybe the fact that the blade lies on its side in the muffle while heating may cause a slight temp imbalance that promotes bending. I will work on a fix for that. I will try the straight edge/tempering fix to deal with the bend in the wakizashi (formerly a katana :) Thanks for the replies....
PS: Grant, evidently not hot enough ;)

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My second katana project just turned into a wakazashi and possible kaiken....I am having a lot of issues with bends and have broken them trying to straighten. Grain looks ok, i have been normalizing 3 times after forging and cleanup. I have not tried to straighten after tempering; i have just heated the area and attempted straightening by gentle hammering and/or hand pressure. Any ideas how i can avoid these problems? Steel is new W1 from Enco forged down from 1 1/2 round. Thanks, Steve

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