A process of forming a fastener with improved threading to resist multi-axial forces and off-axis loading scenarios is provided. The process may include placing first and second mill tools adjacent a shaft of the fastener having a proximal end and a distal end, rotating the shaft and the first and second mill tools, and translating the first and second mill tools along at least part of a length of the shaft to form: a first concave undercut surface oriented toward the proximal end, a first convex undercut surface oriented toward the distal end, a second concave undercut surface oriented toward the distal end, and a second convex undercut surface oriented toward the proximal end.

A fastener with improved threading for resisting multi-axial forces and off-axis loading scenarios is provided. The fastener may include a shaft and a plurality of helical threads disposed about the shaft. The plurality of helical threads may include a first helical thread and a second helical thread adjacent the first helical thread. The first helical thread may include a first concave undercut surface and a first convex undercut surface. The second helical thread may include a second concave undercut surface and a second convex undercut surface. When the fastener is viewed in section along a plane intersecting a longitudinal axis of the shaft, the first concave undercut surface and the second convex undercut surface may be oriented toward the proximal end of the shaft, and the first convex undercut surface and the second concave undercut surface may be oriented toward the distal end of the shaft.

An aircraft assembly having a titanium rod comprising a first threaded portion, and a titanium nut comprising a second threaded portion conforming with the first threaded portion for mating engagement with it. One of the first and second threaded portions defines a male thread and the other one of the first and second threaded portions defines a female thread such that the nut can be wound in threading engagement along the rod. A threaded insert formed from a first metal of different hardness in comparison to titanium is coupled to the rod or the nut to define the first threaded portion or the second threaded portion respectively such that one of the first and second threaded portions is formed from titanium and the other one of the first and second threaded portions is formed from the first metal.

An aircraft assembly having a titanium rod comprising a first threaded portion, and a titanium nut comprising a second threaded portion conforming with the first threaded portion for mating engagement with it. One of the first and second threaded portions defines a male thread and the other one of the first and second threaded portions defines a female thread such that the nut can be wound in threading engagement along the rod. A threaded insert formed from a first metal of different hardness in comparison to titanium is coupled to the rod or the nut to define the first threaded portion or the second threaded portion respectively such that one of the first and second threaded portions is formed from titanium and the other one of the first and second threaded portions is formed from the first metal.

A process of forming a fastener with improved threading to resist multi-axial forces and off-axis loading scenarios is provided. The process may include placing first and second mill tools adjacent a shaft of the fastener having a proximal end and a distal end, rotating the shaft and the first and second mill tools, and translating the first and second mill tools along at least part of a length of the shaft to form: a first concave undercut surface oriented toward the proximal end, a first convex undercut surface oriented toward the distal end, a second concave undercut surface oriented toward the distal end, and a second convex undercut surface oriented toward the proximal end.