BenchReference / Drill sizes / 9.1 mm 9.1 mm Drill Decimal inches 0.3583″
Millimeters 9.1 mm
System Metric
Nearest equivalents in other systems System Nearest drill Size Difference Fractional inch 23/64″ 0.3594″ / 9.128 mm +0.028 mm (+0.0011″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −3.309 mm (−0.1303″)
Letter T 0.3580″ / 9.093 mm −0.007 mm (−0.0003″)
−0.728 mm +0.728 mm 9.1 mm 8.9 mm −0.2 mm 9 mm −0.1 mm 9.2 mm +0.1 mm 9.3 mm +0.2 mm T −0.007 mm 23/64″ +0.028 mm ← #1 −3.309 mm tick position = true diameter · metric neighbors above, equivalents below · window ±0.73 mm
Positive difference = cuts a slightly larger hole than 9.1 mm. Sizes
beyond the window are listed with arrows — they are not close substitutes.
Neighboring metric sizes Drill Decimal in mm vs 9.1 mm 8.9 mm 0.3504 8.9 −0.2 mm 9 mm 0.3543 9 −0.1 mm 9.1 mm 0.3583 9.1 — 9.2 mm 0.3622 9.2 +0.1 mm 9.3 mm 0.3661 9.3 +0.2 mm
← 9 mm (smaller) 9.2 mm (larger) →
Compare 9.1 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 9.1 mm. See all data sources .