According to Shigley and Mischke’s Mechanical Engineering Design (McGraw-Hill 1989) experiments show that the tensile stress supported by a threaded rod equals that of a rod with diameter that is the mean of pitch and minor diameters of the threads. Thus, the tensile stress area of a threaded fastener is computed from the average of its pitch and minor diameters.
- Instock Fasteners provides ANSI/ASME screw thread sizes: ScrewThreadTables
- Little machine shop provides downloadable lists for tap and clearance holes: tapdrillsizes.pdf
- Engineers Edge provides a useful table of thread sizes.
- And large listing of fasteners can be found at SmithFast.