Metric coarse · cutting tap · nominal dimensions
M2 × 0.4
tap drill size.
For M2 × 0.4, the reference drill is 1.6 mm: 0.0630 in (1.600 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 |
|---|---|---|---|---|
| 1/16 | fractional | 1/16 in / 1.587 mm | -0.0005 in | 79.4% |
| #52 | number | 0.0635 in / 1.613 mm | +0.0005 in | 74.5% |
| #53 | number | 0.0595 in / 1.511 mm | -0.0035 in | 94.1% |
| 1.7 mm | metric | 0.0669 in / 1.7 mm | +0.0039 in | 57.7% |
| 1.5 mm | metric | 0.0591 in / 1.5 mm | -0.0039 in | 96.2% |
| #51 | number | 0.0670 in / 1.702 mm | +0.0040 in | 57.4% |
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.