Shirasaya to koshirae conversion for a beefy katana (WIP) May 2, 2021 3:01:51 GMT
Post by Ari on May 2, 2021 3:01:51 GMT
Hi team, long time no see. (: Very pleased that this site is still alive and kicking!
I've recently acquired a very large and heavy katana in shirasaya and am in the process of mounting it. It has a nagasa of 761mm (30") and slight sori. At the habaki it's 9.3mm thick and 37mm wide, at the kissaki 7mm and 26mm respectively. The bare blade weighs approx. 1240 grams (2 3/4 lbs). It's a late Edo period blade and appears to be signed by two students of the Gassan school named Tomoasa and Yoshitsugu. They don't seem to be notable enough to have any of their own entries on online databases. The main appeal of this sword for me was its long length and massive proportions. There is even a bit of ubu ha remaining so it probably hasn't seen much use in its life. Also it's in an old but still attractive polish so I won't have to constantly worry about scuffing it up while I'm working on it.
The shirasaya was nothing special, bit beat up externally but structurally very sound and well carved.
I split them open to clean them out and adjust the fit of the channels, as well as to plug the old mekugi ana and redrill the pilot holes more precisely. The nakago has a hikae mekugi ana which I decided to make use of. The final drilling and tapering will have to wait until I have all the fittings on hand as well as some delrin/acetal rod (None of the susudake pieces I have are thick enough for the diameter of either mekugi ana). From roughly spacing out the diamonds it looks like I can have them enter from alternate sides which seems ideal. At this stage I've profiled the saya and wrapped it in rattan fully. I've also roughly profiled the tsuka and established the flow from the saya that I want.
Because of the dimensions of the blade and corresponding koiguchi size it was impossible to get reproduction or antique fittings to fit. I've made a set of plain fuchi and kashira as well as some hishi motif menuki out of 1.5mm copper sheet. The fuchi is 50mm across its longest measurement! The kashira is 45mm across, and the menuki a more modest 39mm long each. I still have to make the seppa out of the same copper sheet. The tsuba will be a plain ko katchushi style, 95mm across and 3mm thick, but it's still some months away from shipping. The overall koshirae will be quite sparse and utilitarian.
For the next steps I'm mainly waiting for pieces of buffalo horn to arrive so that I can make the koiguchi, kurikata, and kojiri (although I'm tempted to make a rounded copper kojiri instead). I've not really ever had a satisfactory level of hardness from aerosol lacquers in the past so this time around I will try a two-part marine epoxy resin for the saya, same, and tsuka ito.
Thanks for reading and I'll keep this thread updated. (: Ari