An adjustable insert cutting angle cutting tool comprising a tool holder having a cartridge receiving pocket, an insert cartridge clamped the cartridge receiving pocket by a clamping member, and a cutting insert removably retained in the insert cartridge. The clamping member is operated by a separate fastening member. The cutting insert has at least one operative cutting portion, and the insert cartridge is oriented in a cartridge receiving pocket of the tool holder so that the operative cutting portion encounters a workpiece at an insert cutting angle. The clamping member has a clamping surface with at least one clamping zone, and the same at least one clamping zone makes contact with a non-planar clamped surface of the insert cartridge for different values of insert cutting angle. The insert cutting angle is increased or decreased by reorienting the insert cartridge in the tool holder, following release of the fastening member.