Re: Niten Ichi Ryu Bokken
I needed a light bokken for my beginning practice of iaijutsu because of inflamed wrists, and could not find one light enough. I bought a bokken and reduced it in size, planing it and then using an orbital sander. It took forever. Afterwards someone advised me to use a belt sander fixed upside-down, because this reduces the thickness much more quickly than an orbital sander, but is still controllable.
I learned that is is necessary to be careful to reduce the tsuka as well, so that balance is not lost. If this would make the tsuka too thin for your grip, you could always cover it with cord using whipping (in case you haven't seen whipping, you can find it on the web).
Whipping when done neatly is not unlike the binding on a katana, restores the girth of the tsuka, and aids grip. If the whipping is extended part way down the blade, you could fit a tsuba.
Imagine the depth of satisfaction wielding a bokken you had made!
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