A cutter includes radial cutting blades connected by a hinge about which the blades may be rotated between collapsed and extended positions. A rotary body and rotary cap form a handle which holds the inner ends of the blades. The members are mounted for rotation about the hinge axis relative to free blades. Circumferentially spaced stop faces on the body are spaced apart in the axial direction. Circumferentially spaced abutment faces on the cap are spaced apart in the radial direction. The abutment-engaging faces of adjacent free blades are correspondingly spaced apart in the radial direction. To extend the blades, the cap is rotated relative to the body, with the cap and body holding the portions of each free blade between a respective stop face and abutment face for locating the free blades in the extended positions.