Justification of Keyed Joint Fits
О. А. Леонов, N. Zh. Shkaruba, Yu. G. Vergazova, D. U. Khasyanova
Abstract
Cylindrical keyed joint fits used in various assembly units of industrial machinery and agricultural machines have been considered. In most cases, these are clearance, less often, transitional fits due to the assembly and disassembly velocity criterion in this type of connection. In the clearance fits, wear occurs due to the initial relative surface movements, as well as abrasive and wear products occurring in the friction zone. The larger the clearance, the smaller the contact area, the higher the specific pressure, the greater the microshear velocity, the greater the number of contaminants in the contact zone, and the more intensive the surface wear. If there is clearance in the cylindrical fit, the key begins to move along the horizontal and vertical planes, thus leading to increased surface wear and crushing in the key connection with the shaft groove and the bushing groove. Given that the purpose of keyed joints in agricultural machinery is the transmission of large loads, it is recommended to use an interference fit of H7/s7, H8/х8, H8/u8, and H8/s8 to improve the durability substantially. The recommended interference fits have been compared in terms of the interference values in the sprocket shaft joint of the unified reducer H090.20, where 30H7/h9 was earlier used. Even with the highest interference fits, it is possible to dismantle the pressed cylindrical connection using manual pullers.