BenchReference

#55 Drill Bit

Decimal inches 0.0520″
Millimeters 1.321 mm
System Number (wire gauge)

Nearest equivalents in other systems

System Nearest drill Size Difference
Metric 1.3 mm 0.0512″ / 1.3 mm −0.021 mm (−0.0008″)
Fractional inch 3/64″ 0.0469″ / 1.191 mm −0.13 mm (−0.0051″)
Letter A 0.2340″ / 5.944 mm +4.623 mm (+0.1820″)
−0.15 mm+0.15 mm#55#56−0.14 mm#54+0.076 mm3/64″−0.13 mm1.3 mm−0.021 mm← #57 −0.229 mm#53 +0.19 mm →A +4.623 mm →tick position = true diameter · number neighbors above, equivalents below · window ±0.15 mm
Positive difference = cuts a slightly larger hole than #55. Sizes beyond the window are listed with arrows — they are not close substitutes.

Neighboring number sizes

Drill Decimal in mm vs #55
#57 0.0430 1.092 −0.229 mm
#56 0.0465 1.181 −0.14 mm
#55 0.0520 1.321 —
#54 0.0550 1.397 +0.076 mm
#53 0.0595 1.511 +0.19 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 0.0520″. See all data sources.