Tap drill answer
What Size Drill Bit for 3/8-24 UNF Tap?
For a 3/8-24 UNF tap, a common reference drill is Q, which is 0.3320 in or 8.43 mm. Verify the value for material, tap type, and required thread engagement.
3/8-24 UNF tap drill quick answer
Recommended reference drillQ0.3320 in / 8.43 mm
Method: Named UNC and UNF drill sizes are maintained as common cutting-tap reference values and checked against manufacturer ranges. Reviewed 2026-07-24.
How to use this 3/8-24 UNF value
This page gives a common chart value for hand tapping and general reference work. Use a different value when your drawing specifies a thread class, percent thread, forming tap, pipe thread, thin wall, brittle material, or plated/coated part.
- Start with the listed drill size.
- Confirm the tap type and thread engagement target.
- Test in scrap material when fit matters.
- Use cutting fluid and proper chip clearing for deeper holes.
Related references
Tap Drill ChartLook up recommended tap drill sizes for UNC, UNF, and metric threads.Tap Drill CalculatorEstimate tap drill size from major diameter and pitch, then compare to standard drill sizes.Drill and Tap ChartMatch common taps to drill sizes, decimal equivalents, and working notes.Metric Tap Drill ChartReference metric tap drill sizes for M3 through M12 coarse threads.Sources and MethodologyHow this site stores chart values, checks assumptions, and separates reference values from job-specific engineering decisions.