The present disclosure provides a threaded fastener having a hybrid self-drilling tip or drill tip. The fastener includes a head, a shank connected to and extending from the head, a helical thread formation extending radially outwardly from part of the shank, and a self-drilling tip including a first tapered tip portion and a second tapered tip portion. The first tapered tip portion is connected at a first end to the shank and at a second end to the second tapered tip portion, and the second tapered tip portion terminates in a pointed end. The outer diameters of both tapered portions taper radially inwardly moving in the direction of the pointed end, which renders the fastener suitable for attachment to wood as well as for fastening two metal objects to one another.

The object of the invention is a cap to lubricate an inner wall of a perforation going through at least two elements of the structure. The cap comprises a tubular body and at least one lubricant reserve, and before installation in the structure said cap has a largest external diameter larger than an internal diameter (D.sub.S) of the perforation, and the cap lubricates the internal surface of the perforation when its largest external diameter is radially compressed by a wall of the perforation. The invention also concerns a fastener comprising this type of cap, and an interference assembly process for the fastener equipped with the cap. The invention is applicable to the assembly of aircraft structures.

A bone screw, comprising a proximal end and a distal end spaced from the proximal end in a distal direction along a longitudinal axis of the bone screw and a cannulation extending from the proximal end to the distal end. The bone screw further including a threaded region extending along at least a portion of a length of the screw, the length extending from the proximal end to the distal end. The threaded region defining at least one external thread that extends about the longitudinal axis along a helical path. The threaded region includes at least one flute that extends to the distal end of the bone screw. The at least one flute defines an associated at least one cutting tooth that, in turn, defines a cutting face oriented so as to define an angle with respect to the longitudinal axis. The angle is in the range of about 5 degrees and about 25 degrees, and the flute circumferentially interrupts at least a portion of the external thread.

A screw with a flat drilling end comprises a cylinder (1) with a thread (11) wrapped around and a flat drill portion (2) longitudinally extended from a distal end of the cylinder (1); a maximum thickness (T) of a transversal cross section of the flat drill portion (2) being less than a half of the maximum width (D) of the transversal cross section of the flat drill portion (2); the maximum width (D) of the transversal cross section of the flat drill portion (2) being smaller than an outer diameter of the thread (11) of the cylinder (1); the width and thickness of the transversal cross section of the flat dill portion (2) being reduced to a point tip end of the flat drill portion (2). Two opposite lateral sides form as sharp knife blades.

A thread repair insert system having a cylindrical body that extends from an upper end to a lower end and includes a threaded exterior surface and a hollow interior having a threaded interior surface. The lower end of the cylindrical body includes a cutting section that includes a plurality of notches that separate threaded sections. The threaded sections include a cutting edge followed in the direction of rotation by a trailing edge. The lower end also tapers or narrows slightly such that the threaded sections transition from partial threads to full threads as they extend upward. As the thread repair insert is rotated into an opening in parent material, the cutting edge cuts material which is forced between the threads of the threaded sections. As the threaded sections transition from partial threads to full threads in the threaded sections, threads are roll-formed in the parent material.

A fastening bolt includes a shaft defining a central axis, a head, a drilling portion, and first threads alternating with second threads. The first threads and the second threads have different outer diameters. Each first thread has a trailing surface facing the head and inclined to a line perpendicular to the central axis by a trailing angle and a leading surface facing the drilling portion and inclined to the line by a leading angle. The trailing angle is smaller than the leading angle to build an asymmetrical form. Some threads near the drilling portion form respective cutting grooves and recesses thereon. Each cutting groove is formed by walls with different lengths and opened at an angle which does not exceed 90 degrees. The bolt breaks the workpiece quickly by the cutting grooves and recesses. The asymmetrical first threads help enter the workpiece quickly and attain a firm engagement therewith.