Sources and method

Last verified 2026-10-13.

Inch diameters and thread counts follow ASME B1.1. Tap drills use the standard 75% thread chart. Inch clearance holes follow ASME B18.2.8. Metric diameters and pitches follow ISO 261 and ISO 262, with clearance holes from ISO 273. Wood screw pilot holes come from manufacturer guidance and are labelled as guidance because charts disagree.

Each row carries its source. A validation script re-checks the data: the numbered-screw formula, key spot values, and that every drill named in a row exists in the drill tables. The three screw families are never mixed.

This site is a reference, not an engineering specification.