Metric coarse · cutting tap · nominal dimensions
M1.6 × 0.35
tap drill size.
For M1.6 × 0.35, the reference drill is 1.25 mm: 0.0492 in (1.250 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 |
|---|---|---|---|---|
| 1.2 mm | metric | 0.0472 in / 1.2 mm | -0.0020 in | 88.0% |
| 1.3 mm | metric | 0.0512 in / 1.3 mm | +0.0020 in | 66.0% |
| 3/64 | fractional | 3/64 in / 1.191 mm | -0.0023 in | 90.0% |
| #56 | number | 0.0465 in / 1.181 mm | -0.0027 in | 92.1% |
| #55 | number | 0.0520 in / 1.321 mm | +0.0028 in | 61.4% |
| #54 | number | 0.0550 in / 1.397 mm | +0.0058 in | 44.6% |
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.