Drill Bit Size Chart
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Data 2026.07.13-audit.1
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fractional-inch drill · nominal diameter

31/64
drill bit size.

A 31/64 bit measures 0.4844 in across (12.303 mm).

The fractional diameter is exact; decimal and metric values are conversions.

Diameter conversion verified
Calibrated relative diameter · 1 in reference

31/64 · fractional

0.4844 in
12.303 mm
Designation31/64fractional
Inch decimal0.4844nominal
Metric conversion12.303millimetres
Where this size sits from 0 to 1 inch
31/64 · 12.303 mm on a zero to 25.4 millimetre scale. Neighbor marks: 12.3 mm, 12.4 mm.
0 25.4 mm
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Where this bit is specified

What 31/64 is for.

31/64 is the cutting-tap drill for the thread below— usually the reason this size gets looked up. Engagement is calculated from the basic 60° profile; open a thread for its published row, evidence, and limits.

Measured neighbors

What sits beside 31/64.

“Nearest” means nominal diameter only. It does not make a neighboring size acceptable for a tolerance, tapping, reaming, or fastener application.

Source record

Drill Bit Size Chart.

Fractional sizes are exact rational multiples of one inch.

Open source record