when i practice using the shinobi bridge from Bachido, the sharp plastic ridge inevitably leaves ‘teeth marks’ in the san-no-ito, and ive broken 2 so far because of it. I’m not over-straining the strings and all of them are new, so im surprised that such little tension coupled with the bachi strikes can dig that far into the string.
does this happen for anyone else? I’m thinking its because the material is only nylon; would silk strings help perhaps?
This happens to me with my regular koma as well as the shinobi. You could always file it down a bit. The main point of the shinobi koma is that the base touches where the skin is attached to wood.
From my experience it is not the strikes that makes these marks. It’s when you take away the koma which I do every time I stop playing.
For me the string doesn’t snap very fast, and when it does you can always take some of the string that is wound around the itomaki and use the same string. You should be able to do this 2-3 times depending on how much string you used at the knot.
was able to get 3 lengths out of one of them before i conceded and got a new san-no-ito. hopefully that one holds up too.
youre right, it seems to leave an indent in the string as soon as its resting on it, let along being struck. il try filing / rounding it down and report back
Oh snap! (No pun intended) I believe Nitta san sends blank shinobigoma. The player is supposed to file rounded notches into the shinobigoma at their desired spacing just like a normal koma. It should be fine then! 
Oh snap! (No pun intended) I believe Nitta san sends blank shinobigoma. The player is supposed to file rounded notches into the shinobigoma at their desired spacing just like a normal koma. It should be fine then!
mindblown
D=
…
problem solved!