The optimisation of the design of nuts with partly tapered threads

Abstract

The angle of taper and the number of tapered threads in a nut necessary to give the lowest maximum stress concentration in the bolt were determined for an ISO nut—bolt connection subject to axial loading. Thirty-eight frozen stress models were analysed and it was found that a two degree taper for 5.5 threads from the loaded face of the nut reduced the maximum normalised tensile stress in the bolt by 41 per cent from 5.17 to 3.07. It was observed that if the angle of taper was too large the stress concentration produced at the junction of the parallel and tapered threads could negate the beneficial effects of the taper geometry.