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GD&T Building Blocks
Datums
An ideal reference plane, axis, or point used to define dimensions, tolerances, and inspection
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Feature Control Frame
A drawing symbol that defines a feature’s exact geometric tolerance and how it is inspected
Material Condition Modifiers
Specifies how a tolerance applies relative to a feature's size limits - maximum material, least material, or regardless of size
GD&T Symbols
FORM TOLERANCE
Straightness
The permissible deviation on long straight features like the axis of a shaft
FORM TOLERANCE
Flatness
The acceptable variation between the high and low points on a flat surface
FORM TOLERANCE
Roundness
The allowed deviation from a perfect circle on parts with circular cross-sections
FORM TOLERANCE
Cylindricity
The straightness and roundness tolerances of a cylindrical part
ORIENTATION TOLERANCE
Angularity
The acceptable deviation of an angle with the datum being a straight line or plane
ORIENTATION TOLERANCE
Parallelism
The permissible parallel deviation between a line or plane and a datum line or plane
ORIENTATION TOLERANCE
Perpendicularity
The acceptable deviation of a line or plane that's designed as perpendicular to the datum line or plane
LOCATION TOLERANCE
Concentricity
The acceptable deviation between two cylinders that are designed to be concentric about the same central axis
LOCATION TOLERANCE
Coaxiality
The permissible coaxial deviation of the central axis of two cylinders
LOCATION TOLERANCE
Symmetry
The allowable variation between two planes' symmetry
RUN-OUT TOLERANCE
Circular Run-Out
The acceptable deviation of a cylindrical part at any point on its circumference
RUN-OUT TOLERANCE
Total Run-Out
The acceptable deviation of a cylindrical part at any point on its curcumference and along its axis
PROFILE TOLERANCE
Line Profile
The permissible deviation of a curve as viewed from a cross-sectional perspective
PROFILE TOLERANCE
Surface Profile
The acceptable deviation of a surface along its entire surface area
