UNC · cutting tap · nominal dimensions
#6-32 UNC
tap drill size.
For #6-32 UNC, the reference drill is #36: 0.1065 in (2.705 mm).
The reference value is kept separate from the 70% and 75% calculated targets. Actual fit still depends on thread class, tool, material, runout, and the hole you really make.
Detail A · basic 60° profile
What the percentage describes.
“Theoretical full thread %” is radial thread height from nominal geometry. It is not axial engagement length and not a fit-class acceptance measurement.
Real drill alternatives
Neighboring sizes.
These are diameter neighbors, not silent recommendations. A positive delta makes a larger hole and a lower nominal theoretical percentage; a negative delta does the opposite.
| Bit | System | Diameter | Delta | Calculated full thread |
|---|---|---|---|---|
| 2.7 mm | metric | 0.1063 in / 2.7 mm | -0.0002 in | 78.1% |
| #37 | number | 0.1040 in / 2.642 mm | -0.0025 in | 83.8% |
| 7/64 | fractional | 7/64 in / 2.778 mm | +0.0029 in | 70.5% |
| #35 | number | 0.1100 in / 2.794 mm | +0.0035 in | 69.0% |
| 2.8 mm | metric | 0.1102 in / 2.8 mm | +0.0037 in | 68.4% |
| 2.6 mm | metric | 0.1024 in / 2.6 mm | -0.0041 in | 87.8% |
Why 3D is useful here
A thread is a helix, not a row of triangles.
Load a draggable cutaway to see the continuous internal thread. Exact diameter and profile comparisons remain in the 2D drawing above.
Evidence and limits
Why this row says cross-checked.
Tap-drill row: Rows tagged with this source were matched to a named 65% or 75% cutting-tap column. The discrete drill can calculate to a slightly different percentage from nominal dimensions.
60° geometry: Public primary reference for Unified and metric 60-degree thread geometry. The percentage-thread equation is a theoretical basic-profile calculation, not a fit or torque guarantee.
Open National Institute of Standards and Technology geometry source
The repository also records 11 source records and a dataset version on every page.