number drill · nominal diameter

#51
drill bit size.

A #51 bit measures 0.0670 in across (1.702 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

#51 · number

0.0670 in

1.702 mm

Designation#51number

Inch decimal0.0670nominal

Metric conversion1.702millimetres

Where this size sits from 0 to 1 inch

#51 · 1.702 mm on a zero to 25.4 millimetre scale. Neighbor marks: 1.7 mm, #50.

0 25.4 mm

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Measured neighbors

What sits beside #51.

“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

1.7 mmmetric 0.0669 inΔ -0.002 mm 1.8 mmmetric 0.0709 inΔ +0.098 mm 1.6 mmmetric 0.0630 inΔ -0.102 mm 1/16fractional 0.0625 inΔ -0.114 mm

Same seriesNEAREST NOMINAL ROWS

#50number 1.778 mmΔ +0.076 mm #52number 1.613 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

#51drill bit size.

What sits beside #51.

ASME.

#51
drill bit size.