1. BS 4320 is a British Standard that specifies the dimensions and tolerances for metric parallel key and keyways for use in rotating machinery. This standard provides essential guidance for the design and manufacture of keys and keyways, ensuring proper fit and functionality in various applications. Key and keyway combinations are crucial components in transferring power efficiently between shafts and rotating elements, making adherence to BS 4320 of utmost importance in engineering and mechanical industries. By following the requirements outlined in BS 4320, manufacturers can produce key and keyway assemblies that meet the necessary standards for reliability and performance, ultimately contributing to the overall safety and efficiency of machinery and equipment.