# Clearance hole

A cylinder to cut a clearance hole for a metric bolt or screw with. Its axis is along Z, its top face on the XY plane, and it runs down for the depth.

## Source

- **Hole diameter d_h:** ISO 273:1979, Section 2, Dimensions. The table, with fine, medium and coarse series for each thread diameter, is in the official preview: <https://cdn.standards.iteh.ai/samples/4183/1a8db2e6de054d2e9bed7d40be64d6e1/ISO-273-1979.pdf>. The same page gives tolerance fields for information: fine H12, medium H13, coarse H14.
- **Tolerance values:** ISO 286-1 standard tolerance grades IT12, IT13 and IT14, as ELESA+GANTER's Technical Data 10.8 (2018) reproduces them: <https://www.elesa-ganter.in/siteassets/technical/DIN_ISO_286_ISO_Fundamental_Tolerances_EN.pdf>.

An H hole has a lower deviation of 0 and an upper deviation of the grade. So `min` is d_h, `max` is d_h plus the grade, and `mean` is halfway between.

`fit` maps to ISO 273's series: close is fine, normal is medium, loose is coarse. The depth is yours to set; it isn't part of either standard.