Other naming systemsABSOLUTE DIAMETER DELTA
fractional-inch drill · nominal diameter
55/64
drill bit size.
A 55/64 bit measures 0.8594 in across (21.828 mm).
The fractional diameter is exact; decimal and metric values are conversions.
Calibrated relative diameter · 1 in reference
55/64 · fractional
0.8594 in
21.828 mm Designation55/64fractional
Inch decimal0.8594nominal
Metric conversion21.828millimetres
Where this size sits from 0 to 1 inch 55/64 · 21.828 mm on a zero to 25.4 millimetre scale. Neighbor marks: 7/8, 27/32.
Measured neighbors
What sits beside 55/64.
“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