#4-48 UNF Thread
Recommended tap drill #42
Tap drill Ø 0.0935″ / 2.375 mm
Major Ø 0.1120″ / 2.845 mm
Threads per inch 48
The chart recommendation gives approximately 68.4% thread engagement — the conventional target for average materials. It is not the only valid choice; see the options below.
Specification
| Designation | #4-48 UNF |
|---|---|
| Thread family | Unified National Fine (UNF) |
| Nominal size | #4 |
| Basic major diameter | 0.1120″ / 2.845 mm |
| Threads per inch / pitch | 48 TPI (0.529 mm pitch) |
| Recommended tap drill | #42 (0.0935″ / 2.375 mm) |
Tap drill options by thread engagement
Any of these standard drills produces a usable engagement for #4-48 UNF; smaller drills give stronger threads but higher tapping torque. Percentages use the conventional approximation (60° thread form).
| Drill | Decimal in | mm | Approx. engagement |
|---|---|---|---|
| #43 | 0.0890 | 2.261 | 85% |
| 2.3 mm | 0.0906 | 2.3 | 79.3% |
| #42 — chart recommendation | 0.0935 | 2.375 | 68.4% |
| 3/32″ | 0.0938 | 2.381 | 67.4% |
| 2.4 mm | 0.0945 | 2.4 | 64.7% |
Nearest drills to the tap drill in other systems
| Drill | Size | vs #42 | Resulting engagement |
|---|---|---|---|
| 2.4 mm | 0.0945″ / 2.4 mm | +0.025 mm | 64.7% |
| 3/32″ | 0.0938″ / 2.381 mm | +0.006 mm | 67.4% |
Clearance holes
For a bolt or screw of this size to pass through freely. Recommended drills per ASME B18.2.8: close, normal, and loose fits.
Related threads
- #4-40 UNC — same nominal size, 40 TPI (Unified National Coarse (UNC)) · compare
- #3-56 UNF — next size down in UNF
- #5-44 UNF — next size up in UNF