BenchReference

8.5 mm Drill

Decimal inches 0.3346″
Millimeters 8.5 mm
System Metric

Nearest equivalents in other systems

System Nearest drill Size Difference
Fractional inch 21/64″ 0.3281″ / 8.334 mm −0.166 mm (−0.0065″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −2.709 mm (−0.1066″)
Letter Q 0.3320″ / 8.433 mm −0.067 mm (−0.0026″)
−0.68 mm+0.68 mm8.5 mm8.3 mm−0.2 mm8.4 mm−0.1 mm8.6 mm+0.1 mm8.7 mm+0.2 mm21/64″−0.166 mmQ−0.067 mm← #1 −2.709 mmtick position = true diameter · metric neighbors above, equivalents below · window ±0.68 mm
Positive difference = cuts a slightly larger hole than 8.5 mm. Sizes beyond the window are listed with arrows — they are not close substitutes.

Tap drill for

Thread Major diameter Pitch
M10 × 1.5 0.3937″ / 10 mm 1.5 mm

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

Neighboring metric sizes

Drill Decimal in mm vs 8.5 mm
8.3 mm 0.3268 8.3 −0.2 mm
8.4 mm 0.3307 8.4 −0.1 mm
8.5 mm 0.3346 8.5 —
8.6 mm 0.3386 8.6 +0.1 mm
8.7 mm 0.3425 8.7 +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 8.5 mm. See all data sources.