Characteristic And Symbol

Basic definition Tolerance zone shape Datum Refer.

Implied Condition

Allowable Modifiers

Key Points

Flatness

A two dimensional tolerance zone defined by two parallel planes within which the entire surface must lie.

Total width None RFS None

Compares to a perfect counterpoint of itself.

No particular orientation

Straightness

A condition where an element of a surface or an axis is a straight line.

Total width

Cylindrical

None RFS None

Compares to a perfect counterpoint of itself. (e.g. straight line) Additive to size when applied to an axis.

Circularity

A condition on a surface of revolution (cylinder, cone, sphere) where all points of the surface intersected by any plane perpendicular to a common axis (cylinder, cone) or passing through a common center (sphere) are equidistant from the axis of the center.

Total width tolerance

zone between two concentric circles.

None RFS None

Compares to a perfect counterpoint of itself. Not additive to size or location limits.

For

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oler

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s

Cylindricity

A condition on a surface of revolution in which all points of the surface are equidistant from a common axis.

Total width tolerance zone between two

concentric cylinders.

None RFS None

Applies over entire surface. Like wrapping “flatness” around cylinder Very expensive, consider using Runout

Profile of a line

A uniform two dimensional zone limited by two parallel zone lines extending along the length of a feature.

Total width: can be

applied bi-directionally or uni-directionally to either side of profile.

Optional RFS LMC or MMC on datum ref if feature of size

The profile being controlled is defined by Basic dimensions or by equation.

Pro

file

Tol

eran

ces

Profile of a surface

A uniform three dimensional zone contained between two envelope surfaces separated by the tolerance zone across the entire length of a surface.

Total width: can be

applied bi-directionally or uni-directionally to either side of profile.

Optional RFS

LMC or MMC on datum ref if feature of size

(FOS)

The profile being controlled is defined by Basic dimensions or by equation.

Angularity

The distance between two parallel planes, inclined at a specified basic angle, in which the surface, axis, or center plane of the feature must lie.

Total width

Cylindrical

Yes RFS

LMC or MMC on feature if FOS. LMC or MMC on datum ref if FOS

Relation to more than one datum should be considered to stabilize the tolerance zone in more than one direction.

Perpendicularity

The condition of a surface, axis, median plane, or line which is exactly at 90 degrees with respect to a datum plane or axis.

Total width

Cylindrical

Yes RFS

LMC or MMC on feature if FOS. LMC or MMC on datum ref if FOS

Relation to more than one datum should be considered to stabilize the tolerance zone in more than one direction

Ori

enta

tion

Tol

eran

ces

Parallelism

The condition of a surface or axis which is equidistant at all points from a datum of reference.

Total width

Cylindrical

Yes RFS

LMC or MMC on feature if FOS. LMC or MMC on datum ref if FOS

Relation to more than one datum should be considered to stabilize the tolerance zone in more than one direction

Runout: Circular

A composite tolerance used to control the relationship of one or more features of a part to a datum axis during a full 360 degree rotation about the datum axis.

Defined by the full indicator movement (FIM) along an independant circular element when a feature is rotated 360 degrees.

Yes RFS None

Can be defined as the relationship between two features. Relatively inexpensive to implement.

Run

out

Runout: Total

Each circular element of the feature/part must be within the runout tolerance.

Defined by the full indicator movement (FIM) along all circular elements across the entire feature when that feature is rotated 360 degrees.

Yes RFS None

Can be defined as the relationship between two features. Relatively inexpensive to implement.

Loc

atio

n Concentricity

A cylindrical tolerance zone whose axis coincides with the datum axis and within which all cross-sectional axes of the feature being controlled must lie. (Note: Concentricity is very expensive and time-consuming to measure. Recommended that you try position or runout as an alternative tolerance.)

Defined by a cylindrical tolerance zone whose axis coincides with the datum axis and within which all cross-sectional axes of the feature being controlled must lie.

Yes RFS None

Must compare axes. Very epensive to implement. Use position, profile, or runout instead if possible

Loc

atio

n

Position

A zone within which the center, axis, or center plane of a feature of size is permitted ton vary from its true (theoretically exact) position.

Total Width

Cylindrical

Yes RFS

MMC or LMC on the tolerance if the tolerance is applied to a feature of size or on a datum reference if the datum is a feature of size.

With the MMC modifier: Permits functional gage inspection. Allows additional tolerance based upon size. Relatively inexpensive to implement.