Most of the work I do involves repairing, reshaping and re-wrapping tsuka from all kinds of affordable production swords. Even the ones that don’t seem at first to need additional work done require some kind of extra treatment to come out looking and feeling nice. On many of these tsuka, the surprises start once the fittings and old ito are removed to reveal horrors like cracks, rotting wood, knots, shims, patches, fly paper glue strips, and a host of other nasties that you might think were better left unseen.
Some of the above is repairable and workable while some of the worse issues like deep uneven cracks are not. Since many of the shops that make and assemble the furniture for these swords are making tsuka as one size fits all, they tend to overcompensate for a good fit by making them overly thick. While strength is important in a tsuka, it matters little how much it can withstand if it’s too uncomfortable to grip in the first place. A balance of strength and comfort, and in my opinion aesthetics, are needed for a good overall tsuka.
Another challenge that comes up often is adding new fittings that were made in Japan for iaito or Japanese made swords, onto a typically overbuilt Chinese made tsuka. These fittings tend to be much smaller and require a sizable reduction of material before they can fit properly. For the tsukamaki to look even and sit flush with the new fittings on both the ha and mune sides is important for the flow of the tsuka but the reshaping needs to include the omote and ura sides as well. The more you reduce the profile of the ha and mune(while maintaining a proper taper), the more you need to equally reduce the thickness. In cases where there are panels of samegawa, these need to be removed and the channels carved deeper. Not all tsuka can afford this reduction so you need to make sure before you begin this kind of alteration.
You can see in the graphic below the typical production tsuka core (fuchi end) on the left with inlaid samegawa panels. The second image shows with dotted lines the reduction of material from the ha and mune sides. This leaves the core too thick and the samegawa will sit higher than the wood on the edges making for a bulky looking and feeling wrap. In the third image, the samegawa panels have been removed and the channels were carved deeper to allow a uniform reduction of material on all sides.
Here is a real example of a fuchi that was much smaller than the core it was to be fitted to
You can see that the ito would wind up sitting higher than the rim of the fuchi unless material was removed from the ha and mune sides first
As mentioned above, you would also then need to remove material from the omote and ura sides or your tsuka core will be way too thick
I recently worked on a tsuka that needed a complete reshaping and reduction in order to accommodate new smaller fittings. I assessed that there was enough extra material to spare and the reduction would not sacrifice structural integrity. You can see the progression below
This represents the bulk of the work necessary to get an average production katana tsuka in shape before tsukamaki begins