letter drill · nominal diameter

E
drill bit size.

A E bit measures 0.2500 in across (6.350 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

E · letter

0.2500 in

6.350 mm

DesignationEletter

Inch decimal0.2500nominal

Metric conversion6.350millimetres

Where this size sits from 0 to 1 inch

E · 6.350 mm on a zero to 25.4 millimetre scale. Neighbor marks: 6.3 mm, 6.4 mm.

0 25.4 mm

Show calibrated outline Open in Finder

Measured neighbors

What sits beside E.

“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

1/4fractional 0.2500 inΔ +0.000 mm 6.3 mmmetric 0.2480 inΔ -0.050 mm 6.4 mmmetric 0.2520 inΔ +0.050 mm 6.2 mmmetric 0.2441 inΔ -0.150 mm 6.5 mmmetric 0.2559 inΔ +0.150 mm

Same seriesNEAREST NOMINAL ROWS

Dletter 6.248 mmΔ -0.102 mm Fletter 6.528 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

Edrill bit size.

What sits beside E.

ASME.

E
drill bit size.