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    Form

    Form Tolerance (Form Deviation)

    Form tolerance is a basic geometric tolerance that determines the form of the target (part). None of the characteristics of form tolerance require a datum—forms can be independently determined.

    Straightness

    Straightness

    The straightness requirement specifies how perfectly straight a target should be. It is applied to lines and not planes, and represents a curve in the center line or generatrix. Therefore, straightness is used to indicate the warpage tolerance of long objects.

    Sample indication
    Straightness
    Explanation of drawings
    If a tolerance frame is connected to the size indicating the diameter of a cylinder, the axis of that cylinder must be within a cylinder with a diameter of 0.1 mm.

    Flatness

    Flatness

    The flatness requirement specifies the evenness of a surface, or how accurately flat a target plane should be. The most protruding part and the most concaved part must be at a specific distance between two planes that are separated vertically.

    Sample indication
    Flatness
    Explanation of drawings
    This surface must be between two parallel planes separated by only 0.3 mm.

    Roundness

    Roundness

    The roundness requirement specifies how perfectly circular a target—the circular cross-section of a shaft, bore, or cone—should be.

    Sample indication
    Roundness
    Explanation of drawings
    The outer circumference of any cross-section of a shaft cut perpendicularly should be between two concentric circles just 0.1 mm apart on the same plane.

    Cylindricity

    Cylindricity

    The cylindricity requirement specifies how accurately circular and straight a target cylinder is. The value represents any distortion in a cylinder.

    Sample indication
    Roundness
    Explanation of drawings
    The target plane must be between two coaxial cylinders just 0.1 mm apart.

    Profile

    Form Tolerance and Location Tolerance (Profile Tolerance of Line / Profile Tolerance of Plane)

    The profile tolerances of lines and planes are also used in specifying location tolerance. Specifications are indicated in the feature control frame the same way for form tolerance and location tolerance.

    Profile tolerance of line

    Profile tolerance of line

    The profile of the line requirement indicates whether the curvature of a designed part is made to its design. The value indicates any distortion in the profile line (line element that appears on the cross-section of a surface). The cross-section line cutting across the specified curvature must be within the tolerance zone.

    Sample indication
    Profile tolerance of line
    Explanation of drawings
    The target profile on any cross-section parallel to the projection plane must be between the two envelopes created by a circle with a diameter of 0.03 mm and a center on the line having a theoretically exact profile.

    Profile tolerance of plane

    Profile tolerance of plane

    The profile of the plane requirement indicates whether the curvature (surface) of a designed part is made to its design.
    Unlike the profile tolerance of a line, the profile tolerance of the plane involves the entire specified curvature.

    Sample indication
    Profile tolerance of plane
    Explanation of drawings
    The target plane must be between two envelope planes created by a sphere with a diameter of 0.1 mm and a center on the plane having a theoretically exact profile.

    Orientation

    Orientation Tolerance

    Orientation tolerance determines the orientation for the form in relation to a reference. A datum is always necessary to indicate orientation tolerance; as such, it is a geometric tolerance for features related to datums.

    Parallelism

    Parallelism

    While it appears to be similar to flatness, parallelism involves a datum (reference plane or line).
    The parallelism requirement specifies that two lines or planes are parallel.

    Sample indication
    Parallelism
    a Parallel
    Explanation of drawings
    The plane indicated by the indication arrow must be parallel to datum plane A and be between two planes only 0.05 mm apart in the direction of the indication arrows.

    Perpendicularity

    Perpendicularity

    The perpendicularity requirement specifies the accuracy of how perpendicular a target is to the datum (reference plane or line).
    Instead of degrees, millimeters are used as the unit for the value of perpendicularity indication.

    Sample indication
    Perpendicularity
    a Right angle
    Explanation of drawings
    The plane indicated by the indication arrow must be within two parallel planes perpendicular to datum plane A and with a diameter of 0.03 mm.

    Location

    Location Tolerance (Location Deviation)

    Location tolerance determines the location (true position) of the feature in relation to a reference. A datum is always necessary to indicate location tolerance; as such, it is a geometric tolerance for features related to datums.

    True position

    Position

    The true position requirement specifies the accuracy of the position in relation to the datum (reference plane or line).

    Sample indication
    Position
    a Within 0.1 mm dia.
    Explanation of drawings
    The center of the circle indicated by the indication arrow must be within a circle with a diameter of 0.1 mm.

    Coaxiality

    Coaxiality

    The coaxiality requirement specifies the coaxiality of the axes of two cylinders (no deviation of the central axis).

    Sample indication
    Coaxiality
    Explanation of drawings
    The axis of the cylinder indicated by the indication arrow must be within a cylinder with datum axis line A as the axis and a diameter of 0.03 mm.

    Concentricity

    Concentricity

    The concentricity requirement specifies the accuracy of concentricity of the axes of two cylinders (no deviation of the center). Unlike coaxiality, the datum is the center point (plane).

    Sample indication
    Concentricity
    a Within a circle with 0.05 mm dia.
    Explanation of drawings
    The axis of the cylinder indicated by the indication arrow must be within a cylinder with datum axis line A as the axis and a diameter of 0.05 mm.

    Symmetry

    Symmetry

    The symmetry requirement specifies the accuracy of how symmetrical a target is to the datum (reference plane).

    Sample indication
    Symmetry
    a Within 0.05 mm from the theoretical center plane
     
    b Theoretical center plane
    Explanation of drawings
    The center plane indicated by the indication arrow must be between two parallel planes symmetrical to the datum center plane A and separated from each other by 0.05 mm.

    Runout

    Run-out Tolerance (Run-out Deviation)

    Run-out tolerance is a geometric tolerance that specifies the run-out fluctuation of a target’s feature when the target (part) is rotated on an axis (specified straight line). A datum is always necessary to indicate run-out tolerance; as such, it is a geometric tolerance for features related to datums.

    Circular Run-out

    Circular Run-out

    Circular run-out specifies the run-out of any part of a circumference when a part is rotated.
    To meet the circular run-out requirement, the run-out of the measured value when the part is rotated must be within the specified range.

    Sample indication
    Circular Run-out
    Explanation of drawings
    The run-out of the cylindrical surface in the radial direction, indicated by the indication arrow, must not surpass 0.03 mm on any measurement plane perpendicular to the datum axis line when the target is rotated once on the datum axis line.

    Total Run-out

    Total Run-out

    Total run-out specifies the run-out of the entire surface of a part when it is rotated.
    To meet the total run-out requirement, the run-out of the measured value of the entire cylinder surface must be within the specified range.

    Sample indication
    Total Run-out
    Explanation of drawings
    The total run-out of the cylindrical surface in the radial direction, indicated by the indication arrow, must not surpass 0.03 mm at any point on the cylindrical surface when the cylinder part is rotated on the datum axis line.
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