letter drill · nominal diameter

Y
drill bit size.

A Y bit measures 0.4040 in across (10.262 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

Y · letter

0.4040 in

10.262 mm

DesignationYletter

Inch decimal0.4040nominal

Metric conversion10.262millimetres

Where this size sits from 0 to 1 inch

Y · 10.262 mm on a zero to 25.4 millimetre scale. Neighbor marks: 10.3 mm, 13/32.

0 25.4 mm

Show calibrated outline Open in Finder

Measured neighbors

What sits beside Y.

“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

10.3 mmmetric 0.4055 inΔ +0.038 mm 13/32fractional 0.4063 inΔ +0.057 mm 10.2 mmmetric 0.4016 inΔ -0.062 mm 10.4 mmmetric 0.4094 inΔ +0.138 mm 10.1 mmmetric 0.3976 inΔ -0.162 mm

Same seriesNEAREST NOMINAL ROWS

Xletter 10.084 mmΔ -0.178 mm Zletter 10.490 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

Ydrill bit size.

What sits beside Y.

ASME.

Y
drill bit size.