BenchReference

16.5 mm Drill

Decimal inches 0.6496″
Millimeters 16.5 mm
System Metric

Nearest equivalents in other systems

System Nearest drill Size Difference
Fractional inch 21/32″ 0.6563″ / 16.669 mm +0.169 mm (+0.0066″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −10.709 mm (−0.4216″)
Letter Z 0.4130″ / 10.49 mm −6.01 mm (−0.2366″)
−1.32 mm+1.32 mm16.5 mm15.5 mm−1 mm16 mm−0.5 mm17 mm+0.5 mm17.5 mm+1 mm21/32″+0.169 mm← #1 −10.709 mm← Z −6.01 mmtick position = true diameter · metric neighbors above, equivalents below · window ±1.32 mm
Positive difference = cuts a slightly larger hole than 16.5 mm. Sizes beyond the window are listed with arrows — they are not close substitutes.

Tap drill for

Thread Major diameter Pitch
M18 × 1.5 0.7087″ / 18 mm 1.5 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 loose
M14 × 1.5 loose

Neighboring metric sizes

Drill Decimal in mm vs 16.5 mm
15.5 mm 0.6102 15.5 −1 mm
16 mm 0.6299 16 −0.5 mm
16.5 mm 0.6496 16.5 —
17 mm 0.6693 17 +0.5 mm
17.5 mm 0.6890 17.5 +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 16.5 mm. See all data sources.