TABLE OF CONTENTS A machine, in terms of its composition, is an assembly of components and units with specific functions. These components and units must be in specific mating and fitting contacts and assembled to the exact designed positions. Whether a machine operates properly involves many issues such as component designs, manufacturing, quality control, and installation, to name a few. New engineers may wonder: What keeps the shapes of these components exactly as we designed? And what assures the components will stay in place where we want them to be? The answers are: dimensions and tolerances. Dimensions specify the design details that reside in the models, whereas tolerances control the manufacturing and assembly deviations. Both dimensions and tolerances are the key elements in engineering design communication and modeling.
In this chapter, we will introduce types of dimensions, general rules in dimensioning and tolerancing, and preferred engineering practices. We will introduce manufacturing deviations, distributions of these deviations, and standard American National Standards Institute (ANSI) fits. Standard geometric dimensioning and tolerancing controls are briefly introduced as well.
Upon the completion of this chapter, you will be able to:
Identify types of dimensions in engineering design
Dimension features
Understand manufacturing deviations
Understand types of tolerances
Control manufacturing deviations using tolerances
Identify three types of geometric dimensioning and tolerancing (GD&T)
Apply GD&T to a simple design project
An engineering dimension system includes:
Dimensions of size
Dimensions of position
Dimensions of relationships between components in an assembly...
