7/16-20 Tap Drill Size & Thread Specs
Everything for a 7/16-20 UNF thread on one page: tap drill (25/64), clearance holes, wrench and hex key sizes, and the nearest metric thread.
SP-TD-01 · 7/16-20
7/16-20 specs
SizePlate
7/16-20 UNF · tap with
25/64 drill
.3906″
9.92 mm · 72% thread
- Metric drill
- 9.9 mm · .3898
- Clearance
- 29/64 / 15/32
- Wrench
- 5/8″
- Cap screw key
- 3/8″
Thread
- Nominal size
- 7/16″ · 11.11 mm
- Major diameter
- .4375″
- Threads per inch
- 20
- Pitch
- .0500″ · 1.270 mm
- Series
- UNF (fine)
- UNC version
- 7/16-14
Drilling
- Tap drill (75%)
- 25/64 · .3906
- Metric substitute
- 9.9 mm · .3898
- Tap drill (≈50%)
- Y · .4040
- Close fit
- 29/64 · .4531
- Free fit
- 15/32 · .4688
Tools
- Hex bolt wrench
- 5/8″
- Hex nut wrench
- 11/16″
- Socket head cap key
- 3/8″
- Button head key
- —
- Flat head key
- 1/4″
Nearest metric
- Thread
- M12 × 1.75
- Major diameter
- 12 mm
- Pitch
- 1.75 mm
- Tap drill
- 10.2 mm
- Interchangeable
- No
Not interchangeable means the threads look close but won't run together: forcing one into the other strips both.
Drill size by thread percentage
Larger drill, less thread, easier tapping. 75% is the usual target.
| Drill | Decimal | mm | Thread |
|---|---|---|---|
| 9.8 mm | .3858 | 9.8 | 80% |
| W | .3860 | 9.8 | 79% |
| 9.9 mm | .3898 | 9.9 | 73% |
| 25/64 | .3906 | 9.92 | 72% |
| 10 mm | .3937 | 10 | 67% |
| X | .3970 | 10.08 | 62% |
| 10.1 mm | .3976 | 10.1 | 61% |
| 10.2 mm | .4016 | 10.2 | 55% |
| Y | .4040 | 10.26 | 52% |
| 10.3 mm | .4055 | 10.3 | 49% |
| 13/32 | .4063 | 10.32 | 48% |
Neighboring sizes
Questions
What does 7/16-20 mean?
A 7/16″ nominal diameter with 20 threads per inch. It’s the fine (UNF) thread for that size; the coarse version is 7/16-14.
Can I use a 9.9 mm drill instead of 25/64?
Usually. 9.9 mm is .3898″ against .3906″ for 25/64, which changes the thread engagement by a few percent at most. The thread-percentage table above shows exactly how much thread each nearby drill leaves.