The discussion of alignment thus far has been focused on shaft alignment. This chapter and the next one will generalize the subject to encompass the proper orientation of things other than shafts. The definition of alignment in Chapter 1 was:

"Whatever relative orientation of components results in the least amount of vibration or wear."

The term "of components" will be the subject of this chapter, specifically bearings, gears, and pulleys. Shaft-to-shaft alignment orients one major assembly to another in relation to how power is transmitted. These major machine housings are adjustable at their foundations or other attachment points. The orientation of individual components within a machine housing is just as important for proper functioning, but not as easily adjustable.

The geometric features of a component's mounting surface determine its orientation, and the geometric features of the mating part also determine its orientation. These features are roundness, flatness, squareness, and the sizes of diameters for fit. These features are created at the machine tool that shaped the component, and to some extent by the assembly process. The manufacturing process, in general, creates the component alignments, and there is limited adjustment capability in the field. Some shimming or repositioning can be done, but most component alignments reduce to disassembly and rework the geometric features or exchange the bad part. The first step is recognizing poor alignment of components; the intention of this chapter is to provide some diagnostic knowledge.