“E” stands for “envelope.” This symbol indicates the mutual dependency of size tolerance and geometric tolerance. It specifies the envelope of perfect form.
Symbol used by ANSI standard. It represents “Regardless of Feature Size (RFS).” This symbol has been removed in ASME Y14.5-2009.
Indication of tangent plane (ASME only)
“T” stands for “tangent plane.” How angled a plane in contact with the surface is to the datum plane within the range of specified surface is indicated by parallelism. Unlike parallelism, this specifies the convex of the surface and not the concave.
Unequally disposed profile tolerance (ASME only)
“U” stands for “unequally disposed profile.” This specifies the range of run-out of the offset amount from the tolerance zone (tolerance zone limit) in terms of the profile tolerance of a plane. “UZ” is used for annotation according to the ISO standards.
Toleranced feature
Indication of symbols, tolerances, types of geometric tolerances, position, and other requirements.
Movable datum target (ASME only; proposed for ISO)
A specified datum target and other datums associated with it can be moved. For example, even when a part is attached to a target, changing the shape of the target, the datum target and the datum can be moved.
Spot facing (ASME only)
Machining that creates a counterbore enlarges another coaxial hole.
Specification that assigns tolerance to the assembled components according to statistics. By applying statistical tolerance, the tolerance for each component can be increased, reducing the clearance between the components and the mating parts. While this can improve product performance and/or reduce production costs, the application of this tolerance requires appropriate statistical process management as a prerequisite.
