fractional-inch drill · nominal diameter
1/4
drill bit size.
A 1/4 bit measures 0.2500 in across (6.350 mm).
The fractional diameter is exact; decimal and metric values are conversions.
Calibrated relative diameter · 1 in reference
1/4 · fractional
0.2500 in
6.350 mm Designation1/4fractional
Inch decimal0.2500nominal
Metric conversion6.350millimetres
Where this size sits from 0 to 1 inch 1/4 · 6.350 mm on a zero to 25.4 millimetre scale. Neighbor marks: 6.3 mm, 6.4 mm.
Measured neighbors
What sits beside 1/4.
“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