letter drill · nominal diameter

S
drill bit size.

A S bit measures 0.3480 in across (8.839 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

S · letter

0.3480 in

8.839 mm

DesignationSletter

Inch decimal0.3480nominal

Metric conversion8.839millimetres

Where this size sits from 0 to 1 inch

S · 8.839 mm on a zero to 25.4 millimetre scale. Neighbor marks: 8.8 mm, 8.9 mm.

0 25.4 mm

Show calibrated outline Open in Finder

Measured neighbors

What sits beside S.

“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

8.8 mmmetric 0.3465 inΔ -0.039 mm 8.9 mmmetric 0.3504 inΔ +0.061 mm 11/32fractional 0.3438 inΔ -0.108 mm 8.7 mmmetric 0.3425 inΔ -0.139 mm 9 mmmetric 0.3543 inΔ +0.161 mm

Same seriesNEAREST NOMINAL ROWS

Rletter 8.611 mmΔ -0.229 mm Tletter 9.093 mmΔ +0.254 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

Sdrill bit size.

What sits beside S.

ASME.

S
drill bit size.