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7/16-14 tap drill size
Use a U drill (.3680 in / 9.35 mm) to tap 7/16-14 UNC. That gives about 75% thread engagement. Closest metric drill: 9.3 mm.
7/16-14 thread specifications
| Thread | 7/16-14 UNC (coarse) |
|---|---|
| Major (nominal) diameter | .4375 in / 11.11 mm |
| Threads per inch | 14 (pitch 1.814 mm) |
| Theoretical drill for 75% thread | .3679 in (9.34 mm) |
| Recommended tap drill | U = .3680 in |
Alternative drills and % of thread
Any of these drills will tap 7/16-14. Smaller drills give more thread but make tapping harder and raise the risk of breaking the tap, especially in stainless steel and in small sizes. 60–65% thread is common in tough materials. 75% is the general-purpose standard.
| Drill | Inch | mm | % thread |
|---|---|---|---|
| 23/64 | .3594 in | 9.13 | 84% |
| U | .3680 in | 9.35 | 75% |
| 3/8 | .3750 in | 9.53 | 67% |
| V | .3770 in | 9.58 | 65% |
| W | .3860 in | 9.80 | 56% |
| 25/64 | .3906 in | 9.92 | 51% |
Tips for tapping 7/16-14
- Use cutting fluid, and with a hand tap back off about half a turn every turn or two to break the chip. Aluminium and soft materials are the exception: they tap cleanly with spiral-point taps.
- For blind holes, drill deeper than the thread you need. Allow at least 3–4 pitches beyond the last full thread for a plug tap (0.286" for 14 TPI).
- Thread engagement of 1–1.5 × the diameter (11.1–16.7 mm) is enough for most steel parts. Softer materials need more.