This SAE Recommended Practice covers the use of preferred bolt and capscrew sizes, wherever applicable, on construction and industrial machinery to ease serviceability.
Designers, in their efforts to determine the proper fastener for heavy equipment, sometimes overlook the practical aspects of serviceability. When a particular component requires frequent service, it is much faster and easier for the serviceman to work with common size, easily distinguished bolts and capscrews which require a minimum of tools.
Section 4 lists eight diameters of recommended bolts and capscrews, some of which can be found in any hardware store, require only standard tools, are easy to distinguish, and at the same time cover proof loads from 1043 kg (2300 lb) on up at convenient intervals.
While some applications may require other sizes and/or fine threaded fasteners for greater camping forces and/or area restrictions, the convenience of UNC threads in the sizes indicated is preferred wherever possible.