BenchReference

#16 Drill Bit

Decimal inches 0.1770″
Millimeters 4.496 mm
System Number (wire gauge)

Nearest equivalents in other systems

System Nearest drill Size Difference
Metric 4.5 mm 0.1772″ / 4.5 mm +0.004 mm (+0.0002″)
Fractional inch 11/64″ 0.1719″ / 4.366 mm −0.13 mm (−0.0051″)
Letter A 0.2340″ / 5.944 mm +1.448 mm (+0.0570″)
−0.36 mm+0.36 mm#16#18−0.19 mm#17−0.102 mm#15+0.076 mm#14+0.127 mm11/64″−0.13 mm4.5 mm+0.004 mmA +1.448 mm →tick position = true diameter · number neighbors above, equivalents below · window ±0.36 mm
Positive difference = cuts a slightly larger hole than #16. Sizes beyond the window are listed with arrows — they are not close substitutes.

Tap drill for

Thread Major diameter Pitch
#12-24 UNC 0.2160″ / 5.486 mm 24 TPI

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

Neighboring number sizes

Drill Decimal in mm vs #16
#18 0.1695 4.305 −0.19 mm
#17 0.1730 4.394 −0.102 mm
#16 0.1770 4.496 —
#15 0.1800 4.572 +0.076 mm
#14 0.1820 4.623 +0.127 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 number size is 0.1770″. See all data sources.