The comparison does not check fit class, handedness, engagement, coating or gauging requirements.
Evidence and boundaries
What has been checked?
Reviewed 2026-10-19. 66 matching chart rows and the metric/UNC/UNF equations were read directly. The other 27 metric/UNC/UNF sizes have equation estimates only; 18 UNEF sizes have no reviewed drill selection. Calculated conversions are labelled; class-specific manufacturing limits are not supplied.
Public scope only. Nominal sizes are transcribed from the live directory and checked against their designations; paid standard tables were not reviewed.
PDF page 2: 66 matched metric and UNC/UNF rows, CUT TAPS and FORM TAPS columns (55%, 65%, 75%), sizing equations and drilling-runout note. Page 1: numbered and letter drill diameters. Publication revision is not printed on this chart.
Public product page lists B1.1-2024 and its scope. The paid standard tables have not been reviewed here; this reference does not publish class-specific acceptance limits.
Measure at more than one axial position to distinguish taper, then check pitch and thread form. This supports the measurement procedure, not identification from a nominal match.
Historical nominal designation #8 / 0.164 in only. No historical tolerances are used as current acceptance limits.
Metric designations state diameter and pitch in mm. Fractional inch diameters are evaluated exactly; numbered diameters are nominal size values. Inch pitch is 1/TPI in. Metric values use exactly 25.4 mm/in, with display rounding to six decimal places. The reference chart is a general starting point, not a selected tap’s product specification.
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