number drill · nominal diameter

#31
drill bit size.

A #31 bit measures 0.1200 in across (3.048 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

#31 · number

0.1200 in

3.048 mm

Designation#31number

Inch decimal0.1200nominal

Metric conversion3.048millimetres

Where this size sits from 0 to 1 inch

#31 · 3.048 mm on a zero to 25.4 millimetre scale. Neighbor marks: 3 mm, 3.1 mm.

0 25.4 mm

Show calibrated outline Open in Finder

Measured neighbors

What sits beside #31.

“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 mmmetric 0.1181 inΔ -0.048 mm 3.1 mmmetric 0.1220 inΔ +0.052 mm 1/8fractional 0.1250 inΔ +0.127 mm 2.9 mmmetric 0.1142 inΔ -0.148 mm 3.2 mmmetric 0.1260 inΔ +0.152 mm

Same seriesNEAREST NOMINAL ROWS

#32number 2.946 mmΔ -0.102 mm #33number 2.870 mmΔ -0.178 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

#31drill bit size.

What sits beside #31.

ASME.

#31
drill bit size.