number drill · nominal diameter

#27
drill bit size.

A #27 bit measures 0.1440 in across (3.658 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

#27 · number

0.1440 in

3.658 mm

Designation#27number

Inch decimal0.1440nominal

Metric conversion3.658millimetres

Where this size sits from 0 to 1 inch

#27 · 3.658 mm on a zero to 25.4 millimetre scale. Neighbor marks: 3.7 mm, 3.6 mm.

0 25.4 mm

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Measured neighbors

What sits beside #27.

“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

3.7 mmmetric 0.1457 inΔ +0.042 mm 3.6 mmmetric 0.1417 inΔ -0.058 mm 9/64fractional 0.1406 inΔ -0.086 mm 3.8 mmmetric 0.1496 inΔ +0.142 mm 3.5 mmmetric 0.1378 inΔ -0.158 mm

Same seriesNEAREST NOMINAL ROWS

#26number 3.734 mmΔ +0.076 mm #28number 3.569 mmΔ -0.089 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

#27drill bit size.

What sits beside #27.

ASME.

#27
drill bit size.