Importance

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Abstract

An aerospace fastener comprises a blot 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 smooth S-shaped curve with the concave portion preferably having a radius in the range of from 2P to 2.7P. The run-out extends from 1.4P to 2.3P from the maximum grip plane of the bolt, and preferably extends from 1.6P to 2P from the maximum grip plane. The root of the thread in the run-out lies within an envelope defined by boundaries which take into account the maximum and minimum material conditions of the bolt. The nut has a run-in truncating the crest of the nut thread complementary to the run-out to clear the root of the bolt thread when the nut is assembled on the bolt in the minimum grip condition. This permits the nut to be assembled on the bolt further than in a conventional combination, and shortening of the nut and bolt by at least 1P to save weight.

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First Claim