- Orientation Tolerance
Angularity
Angularity is a 3D control; the tolerance zone is two parallel planes. Angularity tolerance applied to a plane surface also controls the flatness on the surface.
- Runout Tolerance
Circular Runout
Circular runout is a 2D surface to axis control. It creates a series of 2D tolerance zones that apply independently. When applied to a cylindrical feature, each tolerance zone is the radial separation between two circles concentric with the datum…
- Form Tolerance
Circularity
Circularity is a 2D tolerance. It controls circular elements, not longitudinal elements. Each circular element of the surface in a plane perpendicular to the axis must lie between two concentric circles, one having a radius 0.03 larger than the other.…
- Form Tolerance
Cylindricity
Cylindricity is the condition of a surface of revolution within which all points of the surface are equidistant from a common axis.
Datum Reference Frame
The Datum Reference Frame (DRF) consists of 3 planes, 3 axes that are mutually perpendicular and intersect at a point. The DRF is the origin of all the basic dimensions and geometric tolerances. If there is no material condition modifier…
Datum vs. Datum Feature
Datum features are the actual, physical features on the part. They are not perfect and will always have manufacturing variation.
Feature Control Frame
The feature control frame (in ASME) or tolerance indicator (in ISO) is the symbolic means of expressing the tolerance requirements for a feature or set of features.
- Form Tolerance
Flatness
Flatness is the condition of a surface having all elements in one plane. A flatness tolerance specifies a tolerance zone defined by two parallel planes within which the surface must lie.
Gear Box Lid and Case
The establishment of a Datum Reference Frame (DRF) and geometric tolerances are based on functional design requirements. If there is no material condition modifier following the feature tolerance, the geometric tolerance applies regardless of feature size (RFS). When RFS applies,…
Index Plate
The establishment of a Datum Reference Frame (DRF) and geometric tolerances are based on functional design requirements. If there is no material condition modifier following the feature tolerance, the geometric tolerance applies regardless of feature size (RFS). When RFS applies,…
LMC Modifier
The least material condition (LMC) of a feature is the biggest hole or smallest pin. An LMC modifier may be applied by placing the circle L symbol in the feature control frame behind the tolerance. This allows additional geometric tolerance…
MMC and LMC
Features of size (such as holes, slots, tabs and pins) have size tolerance that allow them to be big or small within the tolerance limits. There is often a need to refer to a feature at a specific size limit.…
MMC Modifier
The maximum material condition (MMC) of a feature is the smallest hole or biggest pin. An MMC modifier may be applied by placing the circle M symbol in the feature control frame behind the tolerance. This allows additional geometric tolerance…
- Orientation Tolerance
Parallelism
Parallelism is the condition of a surface, axis, or center plane, oriented at 0˚/180˚ to the datum reference frame.
- Orientation Tolerance
Perpendicularity
Perpendicularity is the condition of a surface, median plane, or axis oriented at 90˚ to the datum reference frame.
- Location Tolerance
Position
Position tolerance locates features of size. It defines a tolerance zone within which the feature axis or center plane must lie. The size of this zone determines the amount of variation allowed from true (theoretically exact) position. Basic dimensions establish…
- Location Tolerance
Profile of a Line
Profile of a line specifies a series of 2D cross-sectional tolerance zones along the true profile, within which each 2D surface element must lie. The cross-sections are not compared to each other as a single entity. When used with datum…
- Location Tolerance
Profile of a Surface
By default, profile tolerance specifies a uniform tolerance zone equally distributed about the true profile defined by the basic dimensions. All elements of the surface must lie within the tolerance zone. An arrow from the feature control frame must point…
Size Tolerance and Rule #1
A feature of size is a hole, pin, slot, width, or sphere defined with a plus/minus tolerance.
- Form Tolerance
Straightness Line Elements on a Pin
Straightness - line elements may be applied to the surface of a pin. The specification defines a tolerance zone in which the line elements on the surface must lie. The feature control frame is directed to the surface. MMC and…
- Form Tolerance
Straightness of a Median Line
Straightness of a median line defines a tolerance zone in which the derived median line must lie. When specified at MMC, it defines a virtual condition boundary which the surface must not violate. Note the feature control frame is placed…
Tolerance Zones and Basic Dimensions
A feature control frame creates a geometrically shaped tolerance zone within which the feature must lie. The tolerance zones may be a variety of shapes usually defined by the geometric characteristic in the first compartment and other symbology in the…
- Runout Tolerance
Total Runout
Total runout is a 3D surface to axis control. It creates one tolerance zone that all surface elements must lie within simultaneously. When applied to a cylindrical feature, the tolerance zone is the radial separation between two cylinders coaxial with…