letter drill · nominal diameter

W
drill bit size.

A W bit measures 0.3860 in across (9.804 mm).

The inch decimal is the published nominal designation; millimetres are a conversion.

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

W · letter

0.3860 in

9.804 mm

DesignationWletter

Inch decimal0.3860nominal

Metric conversion9.804millimetres

Where this size sits from 0 to 1 inch

W · 9.804 mm on a zero to 25.4 millimetre scale. Neighbor marks: 9.8 mm, 9.9 mm.

0 25.4 mm

Show calibrated outline Open in Finder

Measured neighbors

What sits beside W.

“Nearest” means nominal diameter only. It does not make a neighboring size acceptable for a tolerance, tapping, reaming, or fastener application.

Other naming systemsABSOLUTE DIAMETER DELTA

9.8 mmmetric 0.3858 inΔ -0.004 mm 9.9 mmmetric 0.3898 inΔ +0.096 mm 9.7 mmmetric 0.3819 inΔ -0.104 mm 25/64fractional 0.3906 inΔ +0.117 mm 10 mmmetric 0.3937 inΔ +0.196 mm

Same seriesNEAREST NOMINAL ROWS

Vletter 9.576 mmΔ -0.229 mm

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

Wdrill bit size.

What sits beside W.

ASME.

W
drill bit size.