Here is what I have found on Ohio knife law. I can't find any reference to blade length.
Ohio - 2923.12. [prohibits carry and concealment of "any
deadly weapon" except for self-defense, without explicit
mention of knives].
- 2923.20 Unlawful transaction in weapons. (A) No person
shall... (3) Manufacture, possess for sale, sell, or
furnish to any other person other than a law enforcement
agency for authorized use in police work, any...
switchblade knife, springblade knife, gravity knife, or
similar weapon...
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Dennis Bible