A drill bushing for a drill unit. In one embodiment, the drill bushing includes a base member having an upper surface, a lower surface configured to rest on a workpiece having a pilot hole, and a retaining member that projects from the lower surface of the base member. The retaining member has a cylindrical outer diameter that fits within the pilot hole. The drill bushing further includes a drill hole that passes from the upper surface of the base member through the retaining member to provide a passage for a drill bit. The drill bushing further includes an expandable slit that passes through the base member and the retaining member to the drill hole, and an adjustment member configured to expand the expandable slit to increase the cylindrical outer diameter of the retaining member within the pilot hole.

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.

A drill bushing for a drill unit. In one embodiment, the drill bushing includes a base member having an upper surface, a lower surface configured to rest on a workpiece having a pilot hole, and a retaining member that projects from the lower surface of the base member. The retaining member has a cylindrical outer diameter that fits within the pilot hole. The drill bushing further includes a drill hole that passes from the upper surface of the base member through the retaining member to provide a passage for a drill bit. The drill bushing further includes an expandable slit that passes through the base member and the retaining member to the drill hole, and an adjustment member configured to expand the expandable slit to increase the cylindrical outer diameter of the retaining member within the pilot hole.

A tool having a flexible shaft, a first end and, a second end and capable of being bent about its axis. The tool transfers rotary motion from a device to tool. The shaft, manufactured from a rigid material, has at least one flexible segment, each flexible segment have at least one sinuous slot ascending in a helical path. With multiple segments, the helical path of the slots can be opposite or the same. With one or more segments having multiple slots, the slots can be parallel or have opposite ascensions, thereby crossing one another. The helical paths can vary within each segment or from segment to segment.

A tool having a flexible shaft, a first end and, a second end and capable of being bent about its axis. The tool transfers rotary motion from a device to tool. The shaft, manufactured from a rigid material, has at least one flexible segment, each flexible segment have at least one sinuous slot ascending in a helical path. With multiple segments, the helical path of the slots can be opposite or the same. With one or more segments having multiple slots, the slots can be parallel or have opposite ascensions, thereby crossing one another. The helical paths can vary within each segment or from segment to segment.

Various embodiments of a flexible drill bit assembly are provided. The flexible drill bit assembly includes structures that allow users to position and direct the flexible drill bit assembly during use and easily interchange components on the ends of the flexible drill bit shaft without requiring additional fasteners, and the flexible drill bit assembly optionally includes a sleave that slides along a flexible shaft of the flexible drill bit assembly.

A fully steerable flexible curved drilling robot device comprises a first flexible tube including a concentric through hole centered on a longitudinal axis, a second flexible tube including an eccentric through hole, wherein the second flexible tube is positioned in the concentric though hole of the first flexible tube, and configured to move translationally along the longitudinal axis and rotationally about the longitudinal axis, and a drill bit connected via a bearing to a flexible drive shaft, the drill bit positioned at a distal end of the first flexible tube, and wherein the flexible drive shaft extends through the eccentric through hole of the second flexible tube and is configured to provide a rotational torque to the drill bit. A steerable flexible curved drilling robot system and drilling method are also disclosed.