BenchReference

9 mm Drill

Decimal inches 0.3543″
Millimeters 9 mm
System Metric

Nearest equivalents in other systems

System Nearest drill Size Difference
Fractional inch 23/64″ 0.3594″ / 9.128 mm +0.128 mm (+0.0050″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −3.209 mm (−0.1263″)
Letter T 0.3580″ / 9.093 mm +0.093 mm (+0.0037″)
−0.72 mm+0.72 mm9 mm8.8 mm−0.2 mm8.9 mm−0.1 mm9.1 mm+0.1 mm9.2 mm+0.2 mmT+0.093 mm23/64″+0.128 mm← #1 −3.209 mmtick position = true diameter · metric neighbors above, equivalents below · window ±0.72 mm
Positive difference = cuts a slightly larger hole than 9 mm. Sizes beyond the window are listed with arrows — they are not close substitutes.

Tap drill for

Thread Major diameter Pitch
M10 × 1 0.3937″ / 10 mm 1 mm

The standard chart recommendation (≈75% thread engagement). Application-specific factors — material, hole depth, tap type — can justify a different drill.

Clearance drill for

Thread Fit
M8 × 1.25 normal
M8 × 1 normal

Neighboring metric sizes

Drill Decimal in mm vs 9 mm
8.8 mm 0.3465 8.8 −0.2 mm
8.9 mm 0.3504 8.9 −0.1 mm
9 mm 0.3543 9 —
9.1 mm 0.3583 9.1 +0.1 mm
9.2 mm 0.3622 9.2 +0.2 mm
Data provenance. ASME B94.11M, Twist Drills (standard drill size series) (ASME). Machinery’s Handbook — tap drill charts (Industrial Press). Millimeter and inch values are converted with the exact definition 1 in = 25.4 mm; the canonical dimension for this metric size is 9 mm. See all data sources.