number drill · nominal diameter
#9
drill bit size.
A #9 bit measures 0.1960 in across (4.978 mm).
The inch decimal is the published nominal designation; millimetres are a conversion.
Calibrated relative diameter · 1 in reference
#9 · number
0.1960 in
4.978 mm Designation#9number
Inch decimal0.1960nominal
Metric conversion4.978millimetres
Where this size sits from 0 to 1 inch #9 · 4.978 mm on a zero to 25.4 millimetre scale. Neighbor marks: 5 mm, #10.
Measured neighbors
What sits beside #9.
“Nearest” means nominal diameter only. It does not make a neighboring size acceptable for a tolerance, tapping, reaming, or fastener application.
Source record
ASME.
The standard text is paywalled. Number and letter series are cross-checked against public manufacturer charts; exact standard edition/page verification remains a release gate.
Open source record