Abstract: An internally expanding cutting device is used for severing large cylindraceous objects in two. The device comprises a spider mechanism in which a series of radially extending arms are attached to a central hub. The spider is arranged to be mounted on a base member so that the spider mechanism is free to rotate. A series of self propelled cutting wheels are mounted on the arms of the spider to allow the cutter wheels to contact the interior wall of the cylinder to be cut. The cutting wheels are arranged to drive the spider in a rotational manner while the cutter wheels are progressively pushed outwardly to deepen the cut. Each wheel follows in the track of the previous cutter wheel until the cylinder is severed.