johns link is a pretty NFA gear clamp, I wager it holds a pretty high psi.
what is your intended application? As I would be pretty sure you could find a gear clamp that would hold a high psi, like A pinhole leak or maybe even a small crack in a pipe but you would need a coupler ( perhaps a barbed type ) involved if your intention is to join 2 high pressure hoses together.
look into hydraulic Lines and companys that deal with them for high psi applications.