Tap drill answer
What Size Drill Bit for 5/16-18 UNC Tap?
For a 5/16-18 UNC tap, a common reference drill is F, which is 0.2570 in or 6.53 mm. Verify the value for material, tap type, and required thread engagement.
5/16-18 UNC tap drill quick answer
Recommended reference drillF0.2570 in / 6.53 mm
How to use this 5/16-18 UNC 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.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.