number drill · nominal diameter

#61
drill bit size.

A #61 bit measures 0.0390 in across (0.991 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

#61 · number

0.0390 in

0.991 mm

Designation#61number

Inch decimal0.0390nominal

Metric conversion0.991millimetres

Where this size sits from 0 to 1 inch

#61 · 0.991 mm on a zero to 25.4 millimetre scale. Neighbor marks: 1 mm, #62.

0 25.4 mm

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Measured neighbors

What sits beside #61.

“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

1 mmmetric 0.0394 inΔ +0.009 mm 0.9 mmmetric 0.0354 inΔ -0.091 mm

Same seriesNEAREST NOMINAL ROWS

#62number 0.965 mmΔ -0.025 mm #60number 1.016 mmΔ +0.025 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

#61drill bit size.

What sits beside #61.

ASME.

#61
drill bit size.