Tolerances¶

The engineering world has developed a large list of different toleration types. The most frequently used types are listed here:

Type	Examples
General Tolerance	`ISO2768-mK`
Approximation	`ca. 5`, `~R5`
Fit	`12js5`
Maximum	`< 14.0`
Minimum	`min. 4.0`
Off-Size	`12.0 +0.1/-0.2`
Reference	`(190.0)`
Theoretically Exact	`[15]`

Tip

If you care about the width of the tolerance (e.g,. for price calculation) and the format of the tolerance does not matter to you, you can simply rely on the IT grade that we calculate for all the tolerances that specify a finite tolerance width. Access it directly through the grade attribute.

General Tolerances¶

General Tolerances are defined in the Title Block and define the tolerances for all measures that do not contain a special tolerance. Different industries use different standards. Currently the following standards are supported:

ISO 2768
DIN 7168

Special Tolerances¶

Special Tolerances are defined directly on the Measure and give drafts person the ability to deviate from the General Tolerances on a specific measure or radius. These special tolerances can be defined in different ways. The following are supported

Approximation¶

When the tolerances are not very important, an approximation tolerance is sometimes used. While we discourage the use of such tolerances, they are frequently used in different industries (e.g., screw manufacturing).

Examples

ca. 10
approx. 10
~ 10

Example Response

        {
            "toleration_type": "APPROXIMATION",
        }

Fit¶

Engineering Fits for shafts and bores typically describe how tight/loose two parts need to fit together. The fit system is based on a "position of the tolerance" (fundamental deviation) and "a width of the tolerance" (tolerance grade).

Examples

10 H7
7 z7

Example Response

    {
        "toleration_type": "FIT_SIZE_ISO",
        "blurb": "H7",
        "deviation_lower": "0.0",
        "deviation_upper": "0.11",
        "fundamental_deviation": "H",
        "tolerance_grade": {
            "grade": 7,
            "warning": null,
        }
    }

Upper and Lower Deviation¶

The upper and lower deviations are calculated from the fit and the nominal size of the measure or radius

Fundamental Deviation¶

The fundamental deviation indicated the position of the tolerance

Tolerance Grade¶

The tolerance grade describes the tolerance width, given the nominal size. For fits they correspond to the width of the number of the fit.

Maximum¶

Maximum tolerances are supported through the tolerance_type MAXIMUM.

Examples

R 5 max
< 100

Example Response

        {
            "toleration_type": "MAXIMUM",
        }

Minimum¶

Minimum tolerances are supported through the tolerance_type MINIMUM.

Examples

Rmin. 5
> 10

Example Response

        {
            "toleration_type": "MINIMUM",
        }

Off-Size¶

Tolerances that are specified through the allowed deviations.

Examples

10 +/- 0.1
2500 +35 -0

Example Response

    {
        "toleration_type": "OFF_SIZE",
        "blurb": "0/+35",
        "deviation_lower": "0.0",
        "deviation_upper": "35.0",
        "fundamental_deviation": "H",
        "tolerance_grade": {
            "grade": 19,
            "warning": "TOLERANCE_WIDTH_LARGER_THAN_NORM",
        }
    }

Fundamental Deviation¶

The fundamental deviation indicated the position of the tolerance

Tolerance Grade¶

The tolerance grade describes the tolerance width, given the nominal size. For fits they correspond to the width of the number of the fit.These tolerance grades are only defined for nominal sized <= 3150mm and are limited to the tolerance grades 1 to 18. Whenever we obtain a value outside that range, we set the warning field to any of the following values:

SIZE_LARGER_THAN_NORM
TOLERANCE_WIDTH_SMALLER_THAN_NORM
TOLERANCE_WIDTH_LARGER_THAN_NORM

Theoretically Exact¶

Theoretically Exact measures are used to describe the norm geometry and are not tolerated.

Example Response

        {
            "toleration_type": "THEORETICALLY_EXACT",
        }