letter drill · nominal diameter

D
drill bit size.

A D bit measures 0.2460 in across (6.248 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

D · letter

0.2460 in

6.248 mm

DesignationDletter

Inch decimal0.2460nominal

Metric conversion6.248millimetres

Where this size sits from 0 to 1 inch

D · 6.248 mm on a zero to 25.4 millimetre scale. Neighbor marks: 6.2 mm, 6.3 mm.

0 25.4 mm

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Measured neighbors

What sits beside D.

“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

6.2 mmmetric 0.2441 inΔ -0.048 mm 6.3 mmmetric 0.2480 inΔ +0.052 mm 1/4fractional 0.2500 inΔ +0.102 mm 6.1 mmmetric 0.2402 inΔ -0.148 mm 6.4 mmmetric 0.2520 inΔ +0.152 mm

Same seriesNEAREST NOMINAL ROWS

Cletter 6.147 mmΔ -0.102 mm Eletter 6.350 mmΔ +0.102 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

Ddrill bit size.

What sits beside D.

ASME.

D
drill bit size.