Shibuichi is strong enough, you can’t use it to cut steel, but as a
jewellery item it will wear fine.
Bronze is also plenty strong enough, of course it depends on the
type of bronze, what elements go into it’s mixture etc. etc. Bell
metal (a pure 80/20) is a brittle as all get out.
Will tiny parts break (?), depends on the parts and how tiny, and
how much stress you exert upon the pieces.
James Binnon has more experience with shibuichi, best to ask him.
Regards Charles A.