BenchReference

15.5 mm Drill

Decimal inches 0.6102″
Millimeters 15.5 mm
System Metric

Nearest equivalents in other systems

System Nearest drill Size Difference
Fractional inch 39/64″ 0.6094″ / 15.478 mm −0.022 mm (−0.0009″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −9.709 mm (−0.3822″)
Letter Z 0.4130″ / 10.49 mm −5.01 mm (−0.1972″)
−1.24 mm+1.24 mm15.5 mm14.5 mm−1 mm15 mm−0.5 mm16 mm+0.5 mm16.5 mm+1 mm39/64″−0.022 mm← #1 −9.709 mm← Z −5.01 mmtick position = true diameter · metric neighbors above, equivalents below · window ±1.24 mm
Positive difference = cuts a slightly larger hole than 15.5 mm. Sizes beyond the window are listed with arrows — they are not close substitutes.

Tap drill for

Thread Major diameter Pitch
M18 × 2.5 0.7087″ / 18 mm 2.5 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
M14 × 2 normal
M14 × 1.5 normal

Neighboring metric sizes

Drill Decimal in mm vs 15.5 mm
14.5 mm 0.5709 14.5 −1 mm
15 mm 0.5906 15 −0.5 mm
15.5 mm 0.6102 15.5 —
16 mm 0.6299 16 +0.5 mm
16.5 mm 0.6496 16.5 +1 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 15.5 mm. See all data sources.