UNC · cutting tap · nominal dimensions
#10-24 UNC
tap drill size.
For #10-24 UNC, the reference drill is #25: 0.1495 in (3.797 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 |
|---|---|---|---|---|
| 3.8 mm | metric | 0.1496 in / 3.8 mm | +0.0001 in | 74.6% |
| #26 | number | 0.1470 in / 3.734 mm | -0.0025 in | 79.4% |
| #24 | number | 0.1520 in / 3.861 mm | +0.0025 in | 70.2% |
| 3.7 mm | metric | 0.1457 in / 3.7 mm | -0.0038 in | 81.9% |
| 3.9 mm | metric | 0.1535 in / 3.9 mm | +0.0040 in | 67.4% |
| #23 | number | 0.1540 in / 3.912 mm | +0.0045 in | 66.5% |
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.