Far too often we'll see a group of people standing around a broken part speculating as to the cause. Then a "person of authority" whether a manager, a senior mechanic, or an engineer, comes along and, without a careful inspection, sagely pronounces that the cause was "such and such". The group agrees with them and then proceeds off on a witch hunt, frequently in the wrong direction. This book is a guide to the basic failure analysis of gears and bearings that can be used by almost everyone involved with machinery maintenance. It describes how the pieces function and the likely failure causes. Then gives outlined steps as to how the physical sources of most, certainly over 80%, of all mechanical failures can be solved in the field with a careful inspection. My hope is that it will see use as a field handbook that makes maintenance more effective.