1-12 Tap Drill Size & Thread Specs
Everything for a 1-12 UNF thread on one page: tap drill (59/64), clearance holes, wrench and hex key sizes, and the nearest metric thread.
SP-TD-01 · 1-12
1-12 specs
SizePlate
1-12 UNF · tap with
59/64 drill
.9219″
23.42 mm · 72% thread
- Metric drill
- 23.5 mm · .9252
- Clearance
- 1-1/64 / 1-1/32
- Wrench
- 1-1/2″
- Cap screw key
- 3/4″
Thread
- Nominal size
- 1″ · 25.4 mm
- Major diameter
- 1.0000″
- Threads per inch
- 12
- Pitch
- .0833″ · 2.117 mm
- Series
- UNF (fine)
- UNC version
- 1-8
Drilling
- Tap drill (75%)
- 59/64 · .9219
- Metric substitute
- 23.5 mm · .9252
- Tap drill (≈50%)
- 61/64 · .9531
- Close fit
- 1-1/64 · 1.0156
- Free fit
- 1-1/32 · 1.0313
Tools
- Hex bolt wrench
- 1-1/2″
- Hex nut wrench
- 1-1/2″
- Socket head cap key
- 3/4″
- Button head key
- —
- Flat head key
- —
Nearest metric
- Thread
- M24 × 3.0
- Major diameter
- 24 mm
- Pitch
- 3 mm
- Tap drill
- 21 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 |
|---|---|---|---|
| 59/64 | .9219 | 23.42 | 72% |
| 23.5 mm | .9252 | 23.5 | 69% |
| 15/16 | .9375 | 23.81 | 58% |
| 24 mm | .9449 | 24 | 51% |
Neighboring sizes
Questions
What does 1-12 mean?
A 1″ nominal diameter with 12 threads per inch. It’s the fine (UNF) thread for that size; the coarse version is 1-8.
Can I use a 23.5 mm drill instead of 59/64?
Usually. 23.5 mm is .9252″ against .9219″ for 59/64, 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.