BenchReference

4.2 mm Drill

Decimal inches 0.1654″
Millimeters 4.2 mm
System Metric

Nearest equivalents in other systems

System Nearest drill Size Difference
Fractional inch 11/64″ 0.1719″ / 4.366 mm +0.166 mm (+0.0065″)
Number (wire gauge) #19 0.1660″ / 4.216 mm +0.016 mm (+0.0006″)
Letter A 0.2340″ / 5.944 mm +1.744 mm (+0.0686″)
−0.336 mm+0.336 mm4.2 mm4 mm−0.2 mm4.1 mm−0.1 mm4.3 mm+0.1 mm4.4 mm+0.2 mm#19+0.016 mm11/64″+0.166 mmA +1.744 mm →tick position = true diameter · metric neighbors above, equivalents below · window ±0.34 mm
Positive difference = cuts a slightly larger hole than 4.2 mm. Sizes beyond the window are listed with arrows — they are not close substitutes.

Tap drill for

Thread Major diameter Pitch
M5 × 0.8 0.1969″ / 5 mm 0.8 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
M3.5 × 0.6 loose

Neighboring metric sizes

Drill Decimal in mm vs 4.2 mm
4 mm 0.1575 4 −0.2 mm
4.1 mm 0.1614 4.1 −0.1 mm
4.2 mm 0.1654 4.2 —
4.3 mm 0.1693 4.3 +0.1 mm
4.4 mm 0.1732 4.4 +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 4.2 mm. See all data sources.