letter drill · nominal diameter

Q
drill bit size.

A Q bit measures 0.3320 in across (8.433 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

Q · letter

0.3320 in

8.433 mm

DesignationQletter

Inch decimal0.3320nominal

Metric conversion8.433millimetres

Where this size sits from 0 to 1 inch

Q · 8.433 mm on a zero to 25.4 millimetre scale. Neighbor marks: 8.4 mm, 8.5 mm.

0 25.4 mm

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Measured neighbors

What sits beside Q.

“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

8.4 mmmetric 0.3307 inΔ -0.033 mm 8.5 mmmetric 0.3346 inΔ +0.067 mm 21/64fractional 0.3281 inΔ -0.098 mm 8.3 mmmetric 0.3268 inΔ -0.133 mm 8.6 mmmetric 0.3386 inΔ +0.167 mm

Same seriesNEAREST NOMINAL ROWS

Rletter 8.611 mmΔ +0.178 mm Pletter 8.204 mmΔ -0.229 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

Qdrill bit size.

What sits beside Q.

ASME.

Q
drill bit size.