The Internal Pressure Pipe Cutter utilizes pump pressure to actuate three carbide-coated knives to cut single and multiple strings of pipe from 4 inches OD to 36 inches OD. Each different size cutter can be dressed with different lengths of knives to cut different sizes of pipe. Pump pressure is preset by a simple adjustment so the knives will extend at the exact desired diameter. Flow restriction across an orifice feeds a piston that forces the knives out. When the knives reach a preset diameter, the operator will see a sudden pressure drop that indicates that the pipe has been cut.