#4-48 Tap Drill Size & Thread Specs
Everything for a #4-48 UNF thread on one page: tap drill (#42), clearance holes, wrench and hex key sizes, and the nearest metric thread.
SP-TD-01 · #4-48
#4-48 specs
SizePlate
#4-48 UNF · tap with
#42 drill
.0935″
2.37 mm · 68% thread
- Metric drill
- 2.4 mm · .0945
- Clearance
- #32 / #30
- Wrench
- 1/4″
- Cap screw key
- 3/32″
Thread
- Nominal size
- #4 · 2.84 mm
- Major diameter
- .1120″
- Threads per inch
- 48
- Pitch
- .0208″ · 0.529 mm
- Series
- UNF (fine)
- UNC version
- #4-40
Drilling
- Tap drill (75%)
- #42 · .0935
- Metric substitute
- 2.4 mm · .0945
- Tap drill (≈50%)
- #40 · .0980
- Close fit
- #32 · .1160
- Free fit
- #30 · .1285
Tools
- Hex bolt wrench
- —
- Hex nut wrench
- 1/4″
- Socket head cap key
- 3/32″
- Button head key
- 1/16″
- Flat head key
- 1/16″
Nearest metric
- Thread
- M3 × 0.5
- Major diameter
- 3 mm
- Pitch
- 0.5 mm
- Tap drill
- 2.5 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 |
|---|---|---|---|
| #43 | .0890 | 2.26 | 85% |
| 2.3 mm | .0906 | 2.3 | 79% |
| #42 | .0935 | 2.37 | 68% |
| 3/32 | .0938 | 2.38 | 67% |
| 2.4 mm | .0945 | 2.4 | 65% |
| #41 | .0960 | 2.44 | 59% |
| #40 | .0980 | 2.49 | 52% |
| 2.5 mm | .0984 | 2.5 | 50% |
| #39 | .0995 | 2.53 | 46% |
Neighboring sizes
Questions
What does #4-48 mean?
A #4 nominal diameter with 48 threads per inch. It’s the fine (UNF) thread for that size; the coarse version is #4-40.
Can I use a 2.4 mm drill instead of #42?
Usually. 2.4 mm is .0945″ against .0935″ for #42, 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.