#3-48 UNC Thread
Recommended tap drill #47
Tap drill Ø 0.0785″ / 1.994 mm
Major Ø 0.0990″ / 2.515 mm
Threads per inch 48
The chart recommendation gives approximately 75.7% thread engagement — the conventional target for average materials. It is not the only valid choice; see the options below.
Specification
| Designation | #3-48 UNC |
|---|---|
| Thread family | Unified National Coarse (UNC) |
| Nominal size | #3 |
| Basic major diameter | 0.0990″ / 2.515 mm |
| Threads per inch / pitch | 48 TPI (0.529 mm pitch) |
| Recommended tap drill | #47 (0.0785″ / 1.994 mm) |
Tap drill options by thread engagement
Any of these standard drills produces a usable engagement for #3-48 UNC; smaller drills give stronger threads but higher tapping torque. Percentages use the conventional approximation (60° thread form).
| Drill | Decimal in | mm | Approx. engagement |
|---|---|---|---|
| #48 | 0.0760 | 1.93 | 85% |
| 5/64″ | 0.0781 | 1.984 | 77.1% |
| #47 — chart recommendation | 0.0785 | 1.994 | 75.7% |
| 2 mm | 0.0787 | 2 | 74.9% |
| 2.05 mm | 0.0807 | 2.05 | 67.6% |
| #46 | 0.0810 | 2.057 | 66.5% |
| #45 | 0.0820 | 2.083 | 62.8% |
| 2.1 mm | 0.0827 | 2.1 | 60.3% |
Nearest drills to the tap drill in other systems
| Drill | Size | vs #47 | Resulting engagement |
|---|---|---|---|
| 2 mm | 0.0787″ / 2 mm | +0.006 mm | 74.9% |
| 5/64″ | 0.0781″ / 1.984 mm | −0.01 mm | 77.1% |
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
- #3-56 UNF — same nominal size, 56 TPI (Unified National Fine (UNF)) · compare
- #2-56 UNC — next size down in UNC
- #4-40 UNC — next size up in UNC