Unified threads per ASME B1.1 formulas. External minor diameters are UNR reference values; V-shape details are
reference geometry. Metric per ISO 965-1 formulas with preferred-number rounding — printed table values may differ
by one rounding step. NPT per ASME B1.20.1. ACME and STI are reference geometry in this version. Always verify
critical dimensions against the governing standard, customer spec, or gauge certificates.