Feature Descriptions
Single-Surface Features
A single-surface feature is a
feature consisting of a single surface that has no opposed points and cannot be considered a
feature of size. (A feature of size must have opposing elements, so an insubstantial cylinder, cone, or sphere cannot be considered a feature of size. See ASME Y14.5-2009, par 1.3.17, or ISO 14660-1.)
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Feature Type
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Icon
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Example
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Description
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Datum Feature?
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Planar Surface
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A single planar surface
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Yes
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Cylindrical Surface
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An insubstantial (≤ 180°) internal or external cylindrical surfaceA
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No
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Conical Surface
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An insubstantial (≤ 180°) internal or external conical surfaceA
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No
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Spherical Surface
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An insubstantial internal or external spherical surface
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No
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Revolved Surface
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An internal or external surface of revolution that is not cylindrical, conical, or spherical
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No
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Extruded Surface
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A surface of extrusion
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No
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General Surface
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A general doubly curving surface
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No
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Single-Surface Features of Size
A single-surface feature of size consists of a single surface with opposed points and is characterized by a size dimension applied to the entire surface or a circular element on the surface. Also, in some cases, two or more complementary surfaces. E.g., a hole feature may be represented in the
CAD model by two semi-cylindrical surfaces that function as cylindrical surface with opposed points and is characterized by a size dimension.
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Feature Type
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Icon
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Example
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Description
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Datum Feature?
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Surface Features of Size
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Simple Hole
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A substantial (>180°) internal cylindrical surfaceA
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Yes
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Shaft
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A substantial (>180°) external cylindrical surfaceA
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Yes
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Ball
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A substantial external spherical surface
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No1
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Socket
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A substantial internal spherical surface
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No1
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Circular Element Features of Size
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Tapered Hole
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A substantial (>180°) internal conical surfaceA
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Yes2
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Tapered Shaft
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A substantial (>180°) external conical surfaceA
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Yes2
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Multi-Surface Features of Size
A multi-surface feature of size consists of multiple related CAD surfaces that are associated with one or more size dimensions.
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Feature Type
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Icon
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Example
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Description
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Datum Feature?
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Special Hole Features
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Blind Hole
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A simple hole with a flat planar depth
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Yes3
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Drilled Hole
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A simple hole with a conical depth
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Yes3
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Multi-Element Hole
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A simple hole, a blind hole, or a drilled hole with one or more additional elements: counterbore, countersink, and/or thread.
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Yes3
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Straight Multi-Surface Features of Size
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Slab
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Externally opposed, overlapping parallel planes
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Yes
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Slot
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Internally opposed, overlapping parallel planes
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Yes
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Slotted Hole
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Opposed planes with cylindrical tangent end caps.
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Yes5
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Tapered Multi-Surface Features of Size
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Tapered Slab
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Externally opposed, overlapping tapered planes centered on a mid-plane
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Yes4
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Tapered Slot
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Internally opposed, overlapping tapered planes centered on a mid-plane
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Yes4
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Tapered Slotted Hole
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Opposed tapered planes with conical tangent end caps.
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Yes6
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Split-draft Multi-Surface Features of Size
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Split-draft Shaft
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Two coaxial Tapered Shaft features that share a common gage circle
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Yes2
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Split-draft Hole
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Two coaxial Tapered Hole features that share a common gage circle
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Yes2
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Split-draft Slab
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Two Tapered Slab features that share a common mid-plane and a common gage width
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Yes4
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Split-draft Slot
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Two Tapered Sot features that share a common mid-plane and a common gage width
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Yes4
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Split-draft Slotted Hole
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Two Tapered Slotted Hole features that share common mid-planes and a common gage width and have the same length
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Yes6
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Multi-Surface Features
A multi-surface group consists of two or more surfaces that cannot be considered a multi-surface feature or size (as described above).
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Feature Type
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Icon
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Example
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Description
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Datum Feature?
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Coplanar Group
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Two or more aligned, coplanar planes
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Yes
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Planar Group
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Two or more parallel planar surfaces that are not aligned and coplanar
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No
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Cocylindrical Group
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Two or more simple holes or two or more shafts that are the same size and are coaxial
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Yes
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Cylindrical Group
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Two or more simple holes or two or more shafts that are coaxial but not the same size
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No
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Extruded Group
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Two or more surfaces that form a feature of extrusion (one translational direction of symmetry)
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No
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Revolved Group
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Two or more surfaces that form a feature of revolution (one rotational direction of symmetry)
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No
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General Group
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Two or more surfaces that form a general feature with no directions of symmetry
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No
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Sheet Metal Features
The following features are specific to sheet metal parts.
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Feature Type
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Icon
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Example
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Description
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Datum Feature?
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Bend Surface
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A cylindrical sheet metal bend surface (≤ 180°)A
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No
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Rolled Surface
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A rolled cylindrical sheet metal surface (>180°)A
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Yes
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Sheet Metal Pair
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A pair of features consisting of a feature that references surfaces from one sheet metal material side and another referencing the opposing surfaces
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No
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When adding features to a sheet metal part, the feature may only reference a consistent set of surfaces referencing only one material side of the sheet metal stock or only edge surfaces.
Patterns
A
pattern consists of two or more features of size with equal size dimensions. A pattern may be either 'linked' or 'unlinked'. Linked patterns are indicated by a
superimposed over the pattern icon (e.g.,
). A linked pattern is directly associated with a feature pattern in the CAD model.
Feature Type | Icon | Description | Datum Feature? |
Pattern | | A collection of similar features of size | Maybe7 |
See
Pattern Descriptions for more detailed information about supported pattern types.
Unsupported Features
The following feature types are not currently supported in this version of GD&T Advisor.
Feature Type | Description | Comments/Workarounds |
Tube or Pipe | Coaxial internal and external cylinders characterized by a thickness | Can be represented by separate Simple Hole and Shaft features, but the thickness dimension cannot be defined |
Torus | A toroidal feature of size | Can be represented by a Revolved Surface, but the size dimensions cannot be defined |
Chamfer | One or more surfaces defined by a line swept along an edge | Typically, the parametric dimensions can be shown for this feature type |
Round or Fillet | One or more surfaces defined by a tangent arc that is swept along an edge | Typically, the parametric dimensions can be shown for this feature type |
Notes
Feature Notes
• A — Although by default, the threshold for a circular feature of size is 180°, the threshold value is specified by the FOS_U_Min application option. See
Setting the System Application Options for more information.
Datum Feature Notes
1. Although allowable according to ASME Y14.5-2009 and ISO 1101:2012, this datum feature type is not supported in this release of application.
2. Datum feature is assumed to be the gage circle of the feature. This datum feature may not be referenced as a primary datum feature in a feature control frame (unless used in conjunction with another coaxial datum feature to define a multiple datum feature, e.g., A-B). May only be referenced in a feature control frame if one of the higher-precedence datum features is a plane that is normal to the feature axis.
3. Datum feature is assumed to be the main hole feature. Other feature surfaces are ignored.
4. Datum feature is assumed to be the opposing line elements on the gage plane of the feature. This datum feature may not be referenced as a primary datum feature in a feature control frame. May only be referenced in a feature control frame if one of the higher-precedence datum features is a plane that is normal to the feature mid-plane.
5. Datum feature is assumed to be the opposing parallel planes. The cylindrical end caps are ignored.
6. Datum feature is assumed to be the opposing line elements on the gage plane of the feature. The conical end caps are ignored. This datum feature may not be referenced as a primary datum feature in a feature control frame. May only be referenced in a feature control frame if one of the higher-precedence datum features is a plane that is normal to the feature mid-plane.
7. Any pattern may be set as a datum feature with the exception of non-parallel axes and non-parallel mid-planes patterns. See
Pattern Descriptions for more information.
