fractional-inch drill · nominal diameter
21/64
drill bit size.
A 21/64 bit measures 0.3281 in across (8.334 mm).
The fractional diameter is exact; decimal and metric values are conversions.
Calibrated relative diameter · 1 in reference
21/64 · fractional
0.3281 in
8.334 mm Designation21/64fractional
Inch decimal0.3281nominal
Metric conversion8.334millimetres
Where this size sits from 0 to 1 inch 21/64 · 8.334 mm on a zero to 25.4 millimetre scale. Neighbor marks: 8.3 mm, 8.4 mm.
Measured neighbors
What sits beside 21/64.
“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