An aerospace fastener comprises a bolt with a roll-formed thread, and a nut with a similar thread having a uniform pitch P. The bolt has a cylindrical shank, a threaded tip and a run-out zone between the shank and tip. The thread root in the run-out follows a concave curve having a radius in the range...http://www.google.fr/patents/US4915559?utm_source=gb-gplus-shareBrevet US4915559 - Lightweight fastener
