BenchReference

#19 Drill Bit

Decimal inches 0.1660″
Millimeters 4.216 mm
System Number (wire gauge)

Nearest equivalents in other systems

System Nearest drill Size Difference
Metric 4.2 mm 0.1654″ / 4.2 mm −0.016 mm (−0.0006″)
Fractional inch 11/64″ 0.1719″ / 4.366 mm +0.149 mm (+0.0059″)
Letter A 0.2340″ / 5.944 mm +1.727 mm (+0.0680″)
−0.337 mm+0.337 mm#19#21−0.178 mm#20−0.127 mm#18+0.089 mm#17+0.178 mm4.2 mm−0.016 mm11/64″+0.149 mmA +1.727 mm →tick position = true diameter · number neighbors above, equivalents below · window ±0.34 mm
Positive difference = cuts a slightly larger hole than #19. Sizes beyond the window are listed with arrows — they are not close substitutes.

Neighboring number sizes

Drill Decimal in mm vs #19
#21 0.1590 4.039 −0.178 mm
#20 0.1610 4.089 −0.127 mm
#19 0.1660 4.216 —
#18 0.1695 4.305 +0.089 mm
#17 0.1730 4.394 +0.178 mm
Data provenance. ASME B94.11M, Twist Drills (standard drill size series) (ASME). Millimeter and inch values are converted with the exact definition 1 in = 25.4 mm; the canonical dimension for this number size is 0.1660″. See all data sources.