number drill · nominal diameter

#50
drill bit size.

A #50 bit measures 0.0700 in across (1.778 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

#50 · number

0.0700 in

1.778 mm

Designation#50number

Inch decimal0.0700nominal

Metric conversion1.778millimetres

Where this size sits from 0 to 1 inch

#50 · 1.778 mm on a zero to 25.4 millimetre scale. Neighbor marks: 1.8 mm, #49.

0 25.4 mm

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Where this bit is specified

What #50 is for.

#50 is the cutting-tap drill for the threads below— usually the reason this size gets looked up. Engagement is calculated from the basic 60° profile; open a thread for its published row, evidence, and limits.

Cutting-tap rows naming #50 CUT TAPS ONLY · CALCULATED ENGAGEMENT

#2-56 UNC UNC · rule-of-thumb row 69.0% calculated thread engagement #2-64 UNF UNF · rule-of-thumb row 78.8% calculated thread engagement

Measured neighbors

What sits beside #50.

“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

1.8 mmmetric 0.0709 inΔ +0.022 mm 1.7 mmmetric 0.0669 inΔ -0.078 mm 1.9 mmmetric 0.0748 inΔ +0.122 mm 1.6 mmmetric 0.0630 inΔ -0.178 mm

Same seriesNEAREST NOMINAL ROWS

#49number 1.854 mmΔ +0.076 mm #51number 1.702 mmΔ -0.076 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

#50drill bit size.

What #50 is for.

What sits beside #50.

ASME.

#50
drill bit size.