The term design means to plan for the construction of an object or the formulation of a plan for the satisfaction of need. The term machine design deals with the design of machines, their mechanisms and elements. Design of Machine Element (DME) may be defined as the selection of material and the dimensions for each geometrical parameter so that the element satisfies its function and undesirable effects are kept within the allowable limit. Machine elements are basic mechanical parts and features used as the building blocks of most machines. This book provides a systematic exposition of the basic concepts and techniques involved in design of machine elements. This book covers design of important elements such as gears, bearings and belt drives. Our hope is that this book, through its careful explanations of concepts, practical examples and figures bridges the gap between knowledge and proper application of that knowledge.