#6-32 UNC Thread
Recommended tap drill #36
Tap drill Ø 0.1065″ / 2.705 mm
Major Ø 0.1380″ / 3.505 mm
Threads per inch 32
The chart recommendation gives approximately 77.6% thread engagement — the conventional target for average materials. It is not the only valid choice; see the options below.
Specification
| Designation | #6-32 UNC |
|---|---|
| Thread family | Unified National Coarse (UNC) |
| Nominal size | #6 |
| Basic major diameter | 0.1380″ / 3.505 mm |
| Threads per inch / pitch | 32 TPI (0.794 mm pitch) |
| Recommended tap drill | #36 (0.1065″ / 2.705 mm) |
Tap drill options by thread engagement
Any of these standard drills produces a usable engagement for #6-32 UNC; smaller drills give stronger threads but higher tapping torque. Percentages use the conventional approximation (60° thread form).
| Drill | Decimal in | mm | Approx. engagement |
|---|---|---|---|
| #37 | 0.1040 | 2.642 | 83.8% |
| 2.7 mm | 0.1063 | 2.7 | 78.1% |
| #36 — chart recommendation | 0.1065 | 2.705 | 77.6% |
| 7/64″ | 0.1094 | 2.778 | 70.5% |
| #35 | 0.1100 | 2.794 | 69% |
| 2.8 mm | 0.1102 | 2.8 | 68.4% |
| #34 | 0.1110 | 2.819 | 66.5% |
| #33 | 0.1130 | 2.87 | 61.6% |
Nearest drills to the tap drill in other systems
| Drill | Size | vs #36 | Resulting engagement |
|---|---|---|---|
| 2.7 mm | 0.1063″ / 2.7 mm | −0.005 mm | 78.1% |
| 7/64″ | 0.1094″ / 2.778 mm | +0.073 mm | 70.5% |
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
- #6-40 UNF — same nominal size, 40 TPI (Unified National Fine (UNF)) · compare
- #5-40 UNC — next size down in UNC
- #8-32 UNC — next size up in UNC