BenchReference

31/64″ Drill Bit

Decimal inches 0.4844″
Millimeters 12.303 mm
System Fractional inch

Nearest equivalents in other systems

System Nearest drill Size Difference
Metric 12.3 mm 0.4843″ / 12.3 mm −0.003 mm (−0.0001″)
Number (wire gauge) #1 0.2280″ / 5.791 mm −6.512 mm (−0.2564″)
Letter Z 0.4130″ / 10.49 mm −1.813 mm (−0.0714″)
−0.984 mm+0.984 mm31/64″29/64″−0.794 mm15/32″−0.397 mm1/2″+0.397 mm33/64″+0.794 mm12.3 mm−0.003 mm← #1 −6.512 mm← Z −1.813 mmtick position = true diameter · fractional neighbors above, equivalents below · window ±0.98 mm
Positive difference = cuts a slightly larger hole than 31/64″. Sizes beyond the window are listed with arrows — they are not close substitutes.

Tap drill for

Thread Major diameter Pitch
9/16″-12 UNC 0.5625″ / 14.287 mm 12 TPI

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
7/16″-14 UNC loose
7/16″-20 UNF loose

Neighboring fractional sizes

Drill Decimal in mm vs 31/64″
29/64″ 0.4531 11.509 −0.794 mm
15/32″ 0.4688 11.906 −0.397 mm
31/64″ 0.4844 12.303 —
1/2″ 0.5000 12.7 +0.397 mm
33/64″ 0.5156 13.097 +0.794 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 fractional size is 0.4844″. See all data sources.