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The Hi-Set Fastening System is a high strength (95 KSI shear) single piece fastener used for automated airframe assembly with squeeze type assembly equipment. As the demands for improved surface quality, shorter cycle times and lower cost increase throughout the airframe industry, automated assembly is becoming more attractive. The design detaiils, installation tooling, installation sequence and cost effectiveness of the Hi-Set are reviewed and compared to other fastening systems.

The metallurgical effects of boron additions to carbon steel are reviewed. Mechanical property data for low carbon-boron steel fasteners is presented and is compared with similar properties for higher carbon steel fasteners. Mechanical property comparisons include data on tensile strength, ductility, toughness, fatigue strength and heat resistance. Mechanical properties of low carbon-boron steel fasteners are shown to be generally equivalent to mechanical properties of higher carbon steel fasteners with two notable exceptions: The ductility of the low carbon steel fasteners is higher than that of the higher carbon steel fasteners at all strength levels, and the heat resistance of the low carbon-boron steels is considerably lower than that of the higher carbon steels.

Corrosion problems associated with using titanium fasteners to assemble aluminum airframe structures are reviewed. Data are presented describing the effectiveness of metallic platings and an aluminum filled organic based coating on fasteners to render the titanium-aluminum electrochemical couple inoperative. The aluminum enriched organic coating known as Hi-Kote 1 is shown to be more effective in minimizing corrosive attack on aluminum airframe structure in both saline and acidic environments. The effectiveness of Hi-Kote 1 in corrosion-fatigue tests of fastened aluminum structure is also reported.