#2-64 Tap Drill Size & Thread Specs
Everything for a #2-64 UNF thread on one page: tap drill (#50), clearance holes, wrench and hex key sizes, and the nearest metric thread.
SP-TD-01 · #2-64
#2-64 specs
SizePlate
#2-64 UNF · tap with
#50 drill
.0700″
1.78 mm · 79% thread
- Metric drill
- 1.8 mm · .0709
- Clearance
- #43 / #41
Thread
- Nominal size
- #2 · 2.18 mm
- Major diameter
- .0860″
- Threads per inch
- 64
- Pitch
- .0156″ · 0.397 mm
- Series
- UNF (fine)
- UNC version
- #2-56
Drilling
- Tap drill (75%)
- #50 · .0700
- Metric substitute
- 1.8 mm · .0709
- Tap drill (≈50%)
- #48 · .0760
- Close fit
- #43 · .0890
- Free fit
- #41 · .0960
Nearest metric
- Thread
- M2 × 0.4
- Major diameter
- 2 mm
- Pitch
- 0.4 mm
- Tap drill
- 1.6 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 |
|---|---|---|---|
| #50 | .0700 | 1.78 | 79% |
| 1.8 mm | .0709 | 1.8 | 75% |
| #49 | .0730 | 1.85 | 64% |
| 1.9 mm | .0748 | 1.9 | 55% |
| #48 | .0760 | 1.93 | 49% |
Neighboring sizes
Questions
What does #2-64 mean?
A #2 nominal diameter with 64 threads per inch. It’s the fine (UNF) thread for that size; the coarse version is #2-56.
Can I use a 1.8 mm drill instead of #50?
Usually. 1.8 mm is .0709″ against .0700″ for #50, 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.