A flexible shaft, having a first end and, a second end and capable of being bent about its axis while transferring rotary motion from a device to tool is disclosed. The shaft, manufactured from a rigid material, has at least one flexible segment having two sinuous slots ascending in a helical path from a common start point in opposite rotational directions. In other segments the slots can be a single helical slot, double helical slots, parallel or crossing, or circumferential. The helical paths can vary within each segment or from segment to segment.
