Geometric Tolerance

Owned by Brian Carter (Unlicensed)
Last updated: May 30, 2012Version comment
3 min read

Available in TurboCAD LTE Pro only


Tolerance is used to specify by how much a dimension can vary. Geometric tolerancing is a way to show maximum allowable deviations of form, profile, orientation, location, and runout of a feature.

The first of two mandatory symbol frames contains a symbol that represents the geometric characteristic to which a tolerance is being applied, such as form, orientation, or runout. Form tolerances control straightness, flatness, circularity, cylindricity, and profiles of lines and surfaces.The second mandatory frame contains the tolerance value. Where applicable, the tolerance value is preceded by a diameter symbol and followed by a material condition symbol.For a tolerance frame with two tolerance values, the second compartments contains the value of Tolerance 1 and is followed by a third, identical compartment that holds the value of Tolerance 2. Other (optional) compartments commonly contain a pair of symbols each. These are a datum reference letter and a material condition symbol.

  1. Select the Tolerance tool.
  2. Click to place the insertion point of the tolerance.
  3. Click to set the angle of the tolerance insertion and to finish.

The Tolerance window provides controls for customizing the symbol frames.


Sym: Select one of the available geometric characteristic symbols.

Tolerance (#): Specify three parameters - the tolerance value and two symbols, diameter and material condition, preceding the value and succeeding it, respectively. The diameter symbol can be inserted by toggling the box preceding the tolerance value field.

MC (Material Conditions): Relevant for features that can vary in size.*Maxi mum material condition (M or MMC):* A feature contains the maximum amount of material stated in the limits. At MMC, a hole has minimum diameter, whereas a shaft has maximum diameter.*Least ma terial condition (L or LMC):* A feature contains the minimum amount of material stated in the limits. At LMC, a hole has maximum diameter, whereas a shaft has minimum diameter.*Rega rdless of Feature Size (S or RFS):* A feature can be any size within the stated limits.

Datum (#): A theoretically point, axis, or plane from which you make measurements and verify dimensions. Usually, two or three mutually perpendicular planes perform this task best. These are jointly called the datum reference frame. Specify one of three datum references - primary, secondary, and tertiary (A, B, and C). The datum reference can consist of a value and a modifying symbol.

Height Protected Tolerance Zone: Controls the variation in height of the extended portion of a fixed perpendicular part and refines the tolerance to that specified by positional tolerances. Enter a value in the data entry field. A projected tolerance zone symbol (P) can be inserted or discarded by toggling the box succeeding the height entry field.Use the Format page to set the parameters for the lines and text of the Tolerance.To edit a tolerance symbol, open its Properties window (see Object Properties) and click Tolerance.