number drill · nominal diameter

#38
drill bit size.

A #38 bit measures 0.1015 in across (2.578 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

#38 · number

0.1015 in

2.578 mm

Designation#38number

Inch decimal0.1015nominal

Metric conversion2.578millimetres

Where this size sits from 0 to 1 inch

#38 · 2.578 mm on a zero to 25.4 millimetre scale. Neighbor marks: 2.6 mm, #39.

0 25.4 mm

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Measured neighbors

What sits beside #38.

“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

2.6 mmmetric 0.1024 inΔ +0.022 mm 2.5 mmmetric 0.0984 inΔ -0.078 mm 2.7 mmmetric 0.1063 inΔ +0.122 mm

Same seriesNEAREST NOMINAL ROWS

#39number 2.527 mmΔ -0.051 mm #37number 2.642 mmΔ +0.063 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

#38drill bit size.

What sits beside #38.

ASME.

#38
drill bit size.