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 1.3.32.1; ASME Y14.5-2018, par. 3.35.2; or ISO 14660-1.)
Feature Type
Icon
Example
Description
Datum Feature?
Planar Surface
A single planar surface
Yes
Cylindrical Surface
An insubstantial (≤ 180°) internal or external cylindrical surfaceA
No
Conical Surface
An insubstantial (≤ 180°) internal or external conical surfaceA
No
Spherical Surface
An insubstantial internal or external spherical surface
No
Revolved Surface
An internal or external surface of revolution that is not cylindrical, conical, or spherical
No
Extruded Surface
A surface of extrusion
No
General Surface
A general doubly curving surface
No
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.
Feature Type
Icon
Example
Description
Datum Feature?
Surface Features of Size
Simple Hole
A substantial (>180°) internal cylindrical surfaceA
Yes
Shaft
A substantial (>180°) external cylindrical surfaceA
Yes
Ball
A substantial external spherical surface
No1
Socket
A substantial internal spherical surface
No1
Circular Element Features of Size
Tapered Hole
A substantial (>180°) internal conical surfaceA
Yes2
Tapered Shaft
A substantial (>180°) external conical surfaceA
Yes2
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.
Feature Type
Icon
Example
Description
Datum Feature?
Special Hole Features
Blind Hole
A simple hole with a flat planar depth
Yes3
Drilled Hole
A simple hole with a conical depth
Yes3
Multi-Element Hole
A simple hole, a blind hole, or a drilled hole with one or more additional elements: counterbore, countersink, and/or thread.
Yes3
Straight Multi-Surface Features of Size
Slab
Externally opposed, overlapping parallel planes
Yes
Slot
Internally opposed, overlapping parallel planes
Yes
Slotted Hole
Opposed planes with cylindrical tangent end caps.
Yes5
Tapered Multi-Surface Features of Size
Tapered Slab
Externally opposed, overlapping tapered planes centered on a mid-plane
Yes4
Tapered Slot
Internally opposed, overlapping tapered planes centered on a mid-plane
Yes4
Tapered Slotted Hole
Opposed tapered planes with conical tangent end caps.
Yes6
Split-draft Multi-Surface Features of Size
Split-draft Shaft
Two coaxial Tapered Shaft features that share a common gage circle
Yes2
Split-draft Hole
Two coaxial Tapered Hole features that share a common gage circle
Yes2
Split-draft Slab
Two Tapered Slab features that share a common mid-plane and a common gage width
Yes4
Split-draft Slot
Two Tapered Sot features that share a common mid-plane and a common gage width
Yes4
Split-draft Slotted Hole
Two Tapered Slotted Hole features that share common mid-planes and a common gage width and have the same length
Yes6
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).
Feature Type
Icon
Example
Description
Datum Feature?
Coplanar Group
Two or more aligned, coplanar planes
Yes
Planar Group
Two or more parallel planar surfaces that are not aligned and coplanar
Yes
Cocylindrical Group
Two or more simple holes or two or more shafts that are the same size and are coaxial
Yes
Cylindrical Group
Two or more simple holes or two or more shafts that are coaxial but not the same size
No
Extruded Group
Two or more surfaces that form a feature of extrusion (one translational direction of symmetry)
No
Revolved Group
Two or more surfaces that form a feature of revolution (one rotational direction of symmetry)
No
General Group
Two or more surfaces that form a general feature with no directions of symmetry
No
Sheet Metal Features
The following features are specific to sheet metal parts.
Feature Type
Icon
Example
Description
Datum Feature?
Bend Surface
A cylindrical sheet metal bend surface (≤ 180°)A
No
Rolled Surface
A rolled cylindrical sheet metal surface (>180°)A
Yes
Sheet Metal Pair
A pair of features consisting of a feature that references surfaces from one sheet metal material side and another referencing the opposing surfaces
No
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 and ISO 1101, 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 common 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.