fractional-inch drill · nominal diameter
25/64
drill bit size.
A 25/64 bit measures 0.3906 in across (9.922 mm).
The fractional diameter is exact; decimal and metric values are conversions.
Calibrated relative diameter · 1 in reference
25/64 · fractional
0.3906 in
9.922 mm Designation25/64fractional
Inch decimal0.3906nominal
Metric conversion9.922millimetres
Where this size sits from 0 to 1 inch 25/64 · 9.922 mm on a zero to 25.4 millimetre scale. Neighbor marks: 9.9 mm, 10 mm.
Measured neighbors
What sits beside 25/64.
“Nearest” means nominal diameter only. It does not make a neighboring size acceptable for a tolerance, tapping, reaming, or fastener application.
This row is at the exposed edge of its series.
Source record
Drill Bit Size Chart.
Fractional sizes are exact rational multiples of one inch.
Open source record