BenchReference / Drill sizes / 8.4 mm 8.4 mm Drill Decimal inches 0.3307″
Millimeters 8.4 mm
System Metric
Nearest equivalents in other systems System Nearest drill Size Difference Fractional inch 21/64″ 0.3281″ / 8.334 mm −0.066 mm (−0.0026″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −2.609 mm (−0.1027″)
Letter Q 0.3320″ / 8.433 mm +0.033 mm (+0.0013″)
−0.672 mm +0.672 mm 8.4 mm 8.2 mm −0.2 mm 8.3 mm −0.1 mm 8.5 mm +0.1 mm 8.6 mm +0.2 mm 21/64″ −0.066 mm Q +0.033 mm ← #1 −2.609 mm tick position = true diameter · metric neighbors above, equivalents below · window ±0.67 mm
Positive difference = cuts a slightly larger hole than 8.4 mm. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Clearance drill for Neighboring metric sizes Drill Decimal in mm vs 8.4 mm 8.2 mm 0.3228 8.2 −0.2 mm 8.3 mm 0.3268 8.3 −0.1 mm 8.4 mm 0.3307 8.4 — 8.5 mm 0.3346 8.5 +0.1 mm 8.6 mm 0.3386 8.6 +0.2 mm
← 8.3 mm (smaller) 8.5 mm (larger) →
Compare 8.4 mm with another size
Data provenance. ASME B94.11M, Twist Drills (standard drill size series) (ASME). Millimeter and inch values are converted with the exact definition 1 in = 25.4 mm; the canonical dimension for this metric size is 8.4 mm. See all data sources .