This book aims at providing an overview of the phenomena of friction in mechanical design. Starting from a research history on this topic, which was crucial since the ancient Egyptians, we pass through the presentation of the first theories proposed by Leonardo da Vinci to reach, the admirable work of Coulomb, the description of some recent mechanical applications in which the precise and accurate knowledge of the coefficients of friction is essential for their correct use and design. Based on the presented investigations some valid methods are proposed in order to measure accurately the coefficients of friction to be used in modern applications such as, for example, the threaded connections and the press-fitted joints mainly applied to front motorbike suspension.