Originally Posted by celtan
So, how did they fit tsubas to the tang? Did they begin with the wood, and once finished , they did the sane-giso and the ito?
And what is more important. How can I adapt a tsuka to the daito's tang without damaging the latter?
From what I've understood, traditionally the wooden grip core parts are carved to fit the tang of a specific sword. When well made, the sword is supposed to be held in the grip by friction, with the mekugi pin being there to help push the sword into the grip, and as a safety feature. Once the grip core has been carved, the two halves of it are glued together, and then all the wrappings and so are done.
I'm not sure how the cast-metal hilts on some WW2-era swords were fitted, but as these would most likely be mated to machine made blades, I guess more uniform tang dimensions, coupled with the fact that the demands on overall quality there seems to have been rather low, could have meant that they could just make these to a certain size and have that fit well enough.
Of course, as many WW2-era swords took considerable shortcuts every here and there, they might have cheated a bit here too. Large amounts of washers (seppa) between grip and tsuba, and between the tsuba and habaki, could indicate that things weren't fitted properly.
I've heard that one thing done by some modern day makers of reproduction katana use rip cores with slightly undersized slots for the tang, and then simply force them on so the wood is compressed, and a suitably sized slot created. Of course, this can make it near impossible to disassemble the sword, and risks cracks and other defects in the grip core.
As for adapting the tsuka from one sword to the tang of another, I'm not sure of this is really done at all, at least not on "real" swords such as this one (the machine made ones with cast grips possibly being another matter). Altering the shape of the tang is as far as I can tell a pretty big no-no under most circumstances, and if you're unwrapping the grip, splitting the core, reshaping the slot (assuming this is even possible), and then reassembling everything (most likely needing new cord to wrap with), then getting an entirely new tsuka made probably isn't much extra effort.