248 terms

GD&T Glossary

3tin3ws.com/gdt_glossary-asme-2009.html (Based on ASME Y14.5-2009)
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Actual Local Size
The measured value of any individual distance at any cross section of a feature of size.
Actual Mating Envelope
This envelope is outside the material. A similar perfect feature(s) counterpart of smallest size that can be contracted about an external feature(s) or largest size that can be expanded within an internal feature(s) so that it coincides with the surface(s) at the highest points. There are two types of actual mating envelopes: related and unrelated.
Actual Minimum Material Envelope
This envelope is within the material. A similar perfect feature(s) counterpart of largest size that can be expanded within an external feature(s) or smallest size that can be contracted about an internal feature(s) so that it coincides with the surface(s) at the lowest points. There are two types of actual mating envelopes: unrelated and related.
All-Around Symbol
The symbolic means of indicating that a tolerance applies to surfaces all around the part is a circle located at the junction of a leader from the feature control frame.
Angularity
The condition of a surface, feature's center plane, or feature's axis at any specified angle from a datum plane or datum axis.
Angularity Tolerance
A tolerance zone defined by two parallel lines, two parallel planes, or a cylinder at a specified basic angle from one or more datum planes or datum axes within which the surface elements, surface, center plane, or axis of the considered feature must lie.
Annotation
Dimensions, tolerances, notes, text, or symbols visible without any manual or external manipulation.
Annotation Plane
A conceptual plane containing annotation that either perpendicularly intersects or is coincident with one or more surfaces of a feature.
Arc
A segment of a curve.
ASME Y14.41-2003
American Society of Mechanical Engineers Standard on Digital Product Definition Data Practices.
ASME Y14.5-2009
The national standard for dimensioning and tolerancing in the United States. ASME stands for American Society of Mechanical Engineers. The Y14.5 is the standard number, and 2009 is the date the standard was officially approved.
ASME Y14.5M-1994
The national standard for dimensioning and tolerancing in the United States. ASME stands for American Society of Mechanical Engineers. The Y14.5 is the standard number. "M" is to indicate the standard is metric, and 1994 is the date the standard was officially approved.
Assembly
A number of parts, or combination thereof, that are joined together to perform a specific function and subject to disassembly without degradation of any of the parts (e.g., power shovel-front, fan assembly, audio frequency amplifier).
Assembly Model
A model in which the product described is an assembly of two or more items.
Associated Entities
The portion of a product definition to which annotation applies.
Associated Group
A user defined set of related digital elements.
Associativity
The established relationship between digital elements.
Attribute
A dimension, tolerance, note, text, or symbol required to complete the product definition or feature of the product that is not visible but available upon interrogating the model.
Attribute Data
Information obtained from an inspection process that indicates only whether a part is acceptable or not acceptable.
Attribute Gage
The family of receiver gages used to collect attributes data; for example, GO and functional gages.
Average Diameter
The average of several diametric measurements across a circular or cylindrical feature.
AVG
Placed near the qualified size dimension where a form control (such as circularity) is specified in a free state. It is then used to ensure that the actual diameter of the feature can be restrained to the desired shape at assembly.
Axis of Feature
A straight line that coincides with the axis of the true geometric counterpart of the specified feature.
Axis Offset
The parallel distance between two axes; for example, the distance between a part feature of size axis and a datum axis.
Axis Theory
When the axis (or center plane) of the feature of size must be within the tolerance zone.
Basic Angle
A type of basic dimension with an angular value used to define the orientation of a part feature or datum target.
Basic Dimension
A theoretically exact dimension.
Between Symbol
A double-ended arrow; replaces the word "BETWEEN" in a note.
Bilateral
Equally Disposed - A uniform boundary tolerance zone that is centered about the true profile.
Bilateral
Unequally Disposed - An unequally disposed tolerance zone is indicated with an unequally disposed profile symbol in the feature control frame following the tolerance value. A second value after the symbol indicates the tolerance in the direction that adds material to the true profile.
Bilateral Tolerance
A type of plus-minus tolerance that allows a dimension to vary in both the plus and minus directions.
Bonus Tolerance
A potential additional tolerance for a geometric control specified at MMC or LMC when considering the effects based on the axis interpretation. Bonus tolerance is the amount the size of the unrelated actual mating envelope departs from MMC, or the amount the unrelated actual minimum material envelope departs from LMC.
Cartoon Gage
A simplified sketch of a functional gage.
Circularity
A condition where all points of a surface of revolution, at any section perpendicular to a common axis, are equidistant from that axis.
Circular Runout
A geometric tolerance that affects the circularity and coaxiality of circular elements of a surface of revolution, or affects the wobble of circular elements of a plane surface perpendicular to a datum axis. It applies independently at each circular measuring position.
Circularity (Roundness)
a) For a feature other than a sphere, all points of the surface intersected by any plane perpendicular to an axis or spine (curved line) are equidistant from that axis or spine. b) For a sphere, all points of the surface intersected by any plane passing through a common center are equidistant from that center.
Circularity Tolerance
A geometric tolerance that specifies a tolerance zone bounded by two concentric circles within which each circular element of the surface must lie.
Circular Runout Control
A geometric tolerance that limits the amount of circular runout of a part surface.
Coaxial Datum Features
Coaxial diameters used to create a single datum axis.
Coaxial Diameters
Two (or more) diameters that are shown on the drawing as being on the same center line (axis).
Coaxiality
The condition where the axes of the unrelated actual mating envelopes, axis of the unrelated minimum material envelope, or median points (as applicable) of one or more surfaces of revolution are coincident.
Commercial and Government Entity (CAGE) Code
A five character code that provides a unique activity identifier used by the government for activity identification.
Composite Position Tolerancing
A multiple-segment feature control frame with one position symbol.
Composite Profile Tolerancing
A multiple-segment feature control frame with one profile symbol.
Concentricity
The condition where the median points of all diametrically opposed elements of a surface of revolution (or the median points of correspondingly located elements of two or more radially disposed features) are congruent with the datum axis (or center point).
Concentricity Tolerance
A cylindrical (or spherical) tolerance zone whose axis (or center point) coincides with the axis (or center point) of the datum feature(s). The median points of all correspondingly located elements of the feature(s) being controlled, regardless of feature size, must lie within the cylindrical (or spherical) tolerance zone.
Conical
A surface of revolution that has a taper symmetrical about its axis. See conical taper.
Conical Taper
The ratio of the difference in the diameters of two sections (perpendicular to the axis) of a cone to the distance between these sections. See ASME Y14.5-2009 paragraph 2.13 for acceptable methods of dimensioning.
Conicity
A profile tolerance applied to a conical surface to control form, or combination of size, form, orientation, and location.
Controlled Radius
A radius with no flats or reversals allowed. Where a controlled radius is specified, it is recommended that the CR be further defined with an engineering control specification (such as a surface texture specification).
Coordinate Tolerancing
A dimensioning system where a part feature is located (or defined) by means of rectangular dimensions with given tolerances.
Coplanar Datum Features
When two or more coplanar surfaces are designated as a single datum plane, simulated by coinciding with the datum feature simulator that simultaneously contacts the high points of two surfaces.
Coplanarity
The condition of two or more surfaces having all elements in one plane.
Copy
Any reproduction or duplication, in any media, of the original.
Counterbore
A cylindrical enlargement of a hole to a specified depth. The bottom of a counterbore is perpendicular to the axis of a hole.
Counterbore Symbol
Symbolic means of indicating a counterbore.
Countersink
A conical shape added to the beginning of a hole. The large diameter of the cone and the included angle are specified along with the countersink symbol.
Countersink Symbol
Symbolic means of indicating a countersink.
Cylindricity
The condition of a surface of revolution in which all points of the surface are equidistant from a common axis.
Cylindricity Control
A cylindricity tolerance specifies a tolerance zone bound by two concentric cylinders within which the surface must lie. A cylindricity control applies simultaneously to both circular and longitudinal elements of the surface.
Data
Information represented in a formal manner suitable for communication, interpretation, or processing by human beings or computers.
Datum
A theoretically exact plane, point or axis from which a dimensional measurement is made.
Datum Axis
The axis of a datum feature simulator established from the datum feature.
Datum Center Plane
The center plane of a datum feature simulator established from the datum feature.
Datum Feature
A feature that is identified with either a datum feature symbol or a datum target symbol.
Datum Feature Reference
The desired order of precedence is indicated by entering the appropriate datum feature reference letter, from left to right, in the feature control frame.
Datum Feature Simulator
Encompasses two types: theoretical and physical.
Datum Plane
A datum established from the datum feature simulator of a nominally flat datum feature. It constrains three degrees of freedom (one translation and two rotations).
Datum Reference Frame
A set of three mutually perpendicular planes, this reference frame exists in theory only and not on the part.
Datum Reference Frame Symbol
A symbol used to label axes of a datum reference frame. The X, Y, Z labels represent the translational degrees of freedom.
Datum Shift
The allowable movement or looseness between the part datum feature and the datum. The datum feature shift / displacement shall always be limited or constrained by the datum feature simulator.
Datum System
A set of symbols and rules that communicate to the drawing user how dimensional measurements are to be made.
Datum Target
The designated point, line, or area used in establishing a datum.
Datum Target Area
Where it is determined that an area is necessary to assure establishment of the simulated datum a datum target area of the desired shape.
Datum Target Identification System
A means of designating a datum target on a drawing. The symbol is paced outside the part outline with a radial line directed to the target.
Datum Target Line
A datum target line is indicated by the target point symbol on an edge view of the surface, a phantom line on the direct view, or both. Where the length of the datum target line must be controlled, its length as well as location are dimensioned.
Datum Target Point
A datum target point is indicated by the target point symbol dimensionally located on a direct view of the surface or, where there is no direct view, dimensioned in two adjacent views.
Depth
Refers to how deep a feature is on a part.
Depth Symbol
Symbolic means of indicating that a dimension applies to the depth of a feature.
Derivative
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Derived Median Line
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Derived Median Plane
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Design Model
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Dial Indicator
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Diameter
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Diameter Symbol
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Die Closure
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Digital Data
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Digital Element
A symbol that describes the shape, size, and location of gage elements that are used to establish datum planes or axes.
Dimension
A numerical value expressed in appropriate units of measure and used to define the size, location, orientation, form, or other geometric characteristics of a part.
Draft
A numerical value expressed in appropriate units of measure and used to define the size, location, orientation, form, or other geometric characteristics of a part.
Drawing
An engineering document or digital data file(s) that discloses (either directly or by reference) by means of graphic or textural presentations, or by combinations of both, the physical or functional requirements of an item.
Drawing Format
The arrangement and organization of information within a drawing. This includes such features as the size and arrangement of blocks, notes, lists, and revision information and the use of optional or supplemental blocks.
Elongated Hole
A hole with a different length and width (commonly referred to as a slot).
Engineering Drawing
A document that communicates a precise description of a part. This description consists of pictures, words, numbers, and symbols.
Equal Bilateral Plus-Minus Tolerance
A tolerance where the allowable variation from the nominal value is the same in both directions.
Feature
A physical portion of a part, such as a surface, pin, hole, or slot or its representation on a drawing, model, or digital data file.
Feature Axis
The axis of the unrelated actual mating envelope of a feature.
Feature Center Plane
The center plane of the unrelated actual mating envelope of a feature.
Feature Control Frame
A rectangular box that is divided into compartments within which the geometric characteristic symbol, tolerance value, modifiers, and datum references are placed.
Feature of Size
One cylindrical or spherical surface, or a set of two opposed elements or opposed parallel surfaces, associated with a size dimension.
First Angle Projection
A dimension that is associated with a feature of size.
Fixed Fastener Assembly
Where the fastener is held in place (restrained) into one of the components of the assembly.
Fixed Fastener Formula
H = F + 2T or T = Where: T = position tolerance diameter H = MMC of the clearance hole H = MMC of the clearance hole F = MMC of the fastener
Flash
A geometric tolerance that limits the amount of flatness error a surface is allowed.
Flatness
The condition of a surface having all of its elements in one plane.
Flatness Tolerance
Specifies a tolerance zone of two parallel planes within which a surface or derived median plane must lie.
Flats
A straight segment that interrupts an arc.
Floating Fastener Assembly
Where all of the components are held together with fasteners (such as nuts and bolts) and both components have clearance holes for the fasteners.
Floating Fastener Formula
A formula used to calculate positional tolerance values in a floating fastener assembly. T = H - F
Where: T = position tolerance diameter (for each part) H = MMC of the clearance hole F= MMC of the fastener
Form Control
A geometric tolerance that limits the amount of form error of a surface, axis, or center plane.
Free State
The condition of a part free of applied forces.
Free State Variation
The distortion of a part after removal of forces applied during manufacture.
FRTZF
Feature related tolerance zone framework.The lower segments of a composite control.
Full Indicator Movement
The total movement of an indicator where appropriately applied to a surface to measure its variations.
Functional Dimensioning
A dimensioning philosophy that defines a part based on how it functions in the final product.
Functional Gage
A fixed limit gage used to verify virtual condition boundaries generated by the collective effect of the feature's maximum material condition and the applicable geometric tolerance at the MMC size.
Fundamental Dimensioning Rules
A set of general rules defined by ASME for dimensioning and interpreting drawings.
Gage
A device used to measure a part characteristic.
Gage Element
A physical portion of a gage.
Gagemakers' Tolerance
The manufacturing tolerance allowed a gagemaker that is applied to gages and comparator setting masters.
Gate
A channel in a mold through which molten material flows into the mold cavity.
Geometric Characteristic Symbols
The symbols that are used to specify the type of geometric control.
Geometric Dimensioning and Tolerancing (GD&T)
An international language used on engineering drawings that consists of well-defined of symbols, rules, definitions and conventions, used on engineering drawings to accurately describe a part. GD&T is a precise mathematical language that can be used to describe the size, form, orientation, and location of part features. GD&T is also a design philosophy on how to design and dimension parts.
Geometric Tolerance
The general term applied to the category of tolerances used to control form, profile, orientation, location, and runout.
Go Gage
A gage that is intended to fit into (for an internal feature of size) or fit over (for an external feature of size) the feature of size.
Great Myth of GD&T
The misconception that geometric tolerancing raises product costs.
Implied 90° Angle
When two lines on a drawing are shown at 90°.
Implied 90° Basic Angle
A 90° basic angle that applies where center lines of features in a pattern (or surfaces shown at right angles on a drawing) are located and defined by basic dimensions, and no angle is specified.
Implied Basic Zero Dimension
Where a center line or center plane of a feature of size is shown in line with a datum axis or center plane. The distance between the center lines or center planes is an implied basic zero.
Implied Datum
An assumed datum.
Implied Parallelism
Where two surfaces are shown parallel on a drawing and the size dimension controls the parallelism between the surfaces.
Implied Self-Datum
When a geometric tolerance implies that a feature is to be inspected relative to its perfect counterpart. Example: a position tolerance specified without a datum reference creates a relationship between the two coaxial features.
Independency
The use of the independency symbol next to the applicable dimension indicates that perfect form of a feature of size at MMC or LMC is not required.
Individual
Notation used along with an indication of the number of places a datum feature and either a single feature of size or a pattern of features of size apply on an individual basis.
Inner Boundary (IB)
A worst-case boundary for an internal feature of size generated by the smallest feature minus the stated geometric tolerance (and any additional tolerance, if applicable).
Irregular Feature of Size
A general term for two types of irregular features of size. Type A: a directly toleranced feature or collection of features that may contain or be contained by an actual mating envelope that is a sphere, cylinder, or pair of parallel planes.Type B: a directly toleranced feature or collection of features that may contain or be contained by an actual mating envelope other than a sphere, cylinder, or pair of parallel planes.
Item
A nonspecific term used to denote any unit or product, including materials, parts, assemblies, equipment, accessories, and computer software.
Item Identification
The part, identifying number, or descriptive identifier for a specific item along with the original design activity identification.
Least Material Boundary
The limit defined by a tolerance or combination of tolerances that exists on or inside the material of a feature(s).
Least Material Condition
The condition in which a feature of size contains the least amount of material everywhere within the stated limits of size.
Limits of Size
The specified maximum and minimum sizes.
Location
a) Center to center distance between features of size. b) Location of features of size from a datum. c) Coaxiality of features of size. d) Concentricity or symmetry of features of size from a datum axis or plane.
Maximum Material Boundary
The limit defined by a tolerance or combination of tolerances that exist on or outside of the feature(s).
Maximum Material Condition
The condition in which a feature of size contains the maximum amount of material everywhere within the stated limits of size.
May
Used when it is necessary to express nonmandatory provisions.
Measurement Uncertainty
The difference between the corrected measured size and the actual size. In cases where there is adequate information based on a statistical distribution, the estimate may be associated with a specific probability.
Median Point
The mid-point of a two-point measurement.
Mismatch
The offset of features on a part caused by misalignment of opposing segments of a mold or die.
Model
A combination of design model, annotation, and attributes that describes a product..
Modifiers
Symbols that define conditions for the tolerance zone of a geometric control or a part condition for inspection.
Monodetail Drawing
Delineates a single part.
Movable Datum Target
A datum target with a movable datum target datum feature simulator.
Movable Datum Target Symbol
May be used to indicate movement of the datum target datum feature simulator. The movable datum target symbol, though not required, may be used for clarity.
Multidetail Drawing
Delineates two or more uniquely identified parts in separate views or in separate sets of views on the same drawing.
Multiple Single-Segment
When two (or more) single-segment feature control frames are stacked together. Each segment is an independent requirement.
No-Go Gage
A gage that is not intended to fit into or over a feature of size. A No-Go gage is made to the LMC limit of the feature of size.
Nominal Size
The designation used for purposes of general identification.On a drawing, it is the specified value of a dimension.
Non-Feature of Size
Not considered a feature of size because the parallel surfaces are not opposed; they are offset..
Nonuniform
A maximum material boundary and least material boundary, or a unique shape, that encompasses the true profile. Where used, the term NON-UNIFORM replaces the tolerance value in the profile feature control frame.
Opposed
Placed directly across from an element or surface.
Orientation
The orientation of a feature or a feature of size is its angular relationship to a datum. Orientation tolerances control parallel, perpendicular, and all other angular relationships..
Orientation Control
A geometric tolerance that limits the amount of orientation error a surface, axis, or center plane is allowed.
Outer Boundary (OB)
A worst-case boundary for an external feature of size generated by the largest feature plus the stated geometric tolerance (and any additional tolerance, if applicable).
Parallel
The condition of being an equal distance apart at every point.
Parallelism
The condition of a surface or center plane equidistant at all points of a datum plane, or an axis equidistant along its length from one or more datum planes or a datum axis.
Parallelism Control
A geometric tolerance that limits the amount a surface, axis, or center plane is permitted to vary from being parallel to the datum. Orientation tolerances are constrained only in rotational degrees of freedom relative to referenced datums.
Part
One item, or two or more items joined together, not normally subject to disassembly without destruction or impairment of designed use.
Part or Identification Number
The identifier assigned by the original design activity, or by the controlling nationally recognized standard, that uniquely identifies a specific item relative to that design activity.
Parting Line
a) The separation between the mold or die segments, flash fins, or material seepage is usually produced on the part periphery where the parting line emerges. b) A line on the drawing representing the mated surfaces of the die or mold segments.
Pattern
Two or more features or features of size to which a locational tolerance is applied that are grouped by one of the following methods: nX, nCOAXIAL HOLES, ALL OVER, the between symbol,nSURFACES, SIMULTANEOUS REQUIREMENTS, or INDICATED.
Perpendicular
A surface, center plane, or axis at a right angle to a datum plane or axis.
Perpendicularity
The condition of a surface, axis, or center plane being exactly 90° to a datum.
Perpendicularity Control
A geometric tolerance that limits the amount a surface, axis, or center plane is permitted to vary from being 90° to the datum. Orientation tolerances are constrained in rotational degrees of freedom relative to the referenced datums.
Phantom Line
A line consisting of a pattern of a long dash, two short dashes, and a long dash.
Physical Datum Feature Symbol
The physical boundary used to establish a simulated datum from a specified datum feature.
Planar Feature of Size
A feature of size that contains two features: the two parallel plane surfaces (such as a width or a thickness). A planar feature of size is one type of a regular feature of size; capable of producing a center plane.
PLTZF
Pattern locating tolerance zone framework. The uppermost segment of a composite position control. The basic relationship between the features in a pattern and the referenced datums.
Plus-minus Tolerance
Where the nominal of the dimension is given first, followed by a plus-minus expression of a tolerance.
Polygon
A closed plane figure with straight sides.
Position Tolerance
A zone for the axis or center plane, or a virtual condition boundary located at the true position.
Primary Datum
The first datum plane that the part contacts in a dimensional measurement.
Profile
The outline of a surface, a shape made up of one or more features, or a two-dimensional element of one or more features.
Profile Control
A geometric tolerance that is used to define a tolerance zone to control form or combinations of size, form, orientation, and location of a feature relative to a true profile.
Profile of a Line Control
A geometric tolerance that specifies a two-dimensional requirement and that the tolerance zone is normal to the true profile of the feature at each line element.
Profile of a Surface Control
A geometric tolerance that specifies a three-dimensional requirement extending along the length and width of the considered feature or features.
Projected Tolerance Zone
A tolerance zone that is projected above the part surface. A projected tolerance zone is recommended where variations in perpendicularity of threads or press-fit holes could cause fasteners to interfere with mating parts.
Radius
A straight line extending from the center to the periphery of a circle or sphere.
Reference Dimension
a) A repeat of a dimension b) A dimension derived from other values shown on the drawing or on related drawings. One method for identifying a reference dimension on drawings is to enclose the dimension within parentheses.
Regardless of Feature Size
The term that indicates a geometric tolerance or datum reference applies at any increment of size of the actual mating envelope of the feature of size.
Regardless of Material Boundary
Indicates that a datum feature simulator progresses from the MMB to the LMB until it makes contact with the extremities of a feature(s).
Regular Feature of Size
One cylindrical or spherical surface, a circular element, and a set of two parallel elements or opposed parallel surfaces, each of which is associated with a directly toleranced dimension.
Related Actual Mating Envelope
A similar perfect feature counterpart expanded within an internal feature(s) or contracted about an external feature(s) while constrained within orientation or location (or both) to the applicable datum(s).
Related Actual Minimum Material Envelope
A similar perfect feature counterpart contracted about an internal feature(s) or expanded within an external feature(s) while constrained within orientation or location (or both) to the applicable datum(s).
Restraint
The application of force(s) to a part to simulate its assembly or functional condition resulting in possible distortion of a part from its free-state condition.
Reversal
A change of direction (or interruption) of the surface of the arc (i.e. a tool mark).
Rule #1
The form of an individual regular feature of size is controlled by the limits of size to the extent prescribed in the following paragraphs:

a)The surface or surfaces of a regular feature of size shall not extend beyond a boundary of perfect form at MMC. This boundary is the true geometric form represented on the drawing. No variation in form is permitted if the regular feature of size is produced at its MMC limit of size unless a straightness or flatness tolerance is associated with the size dimension or the independency symbol is applied.

b) Where the actual local size of a regular feature of size has departed from MMC towards LMC, a local variation in form is allowed equal to the amount of such departure.

c) There is no default requirement for a boundary of perfect form at LMC. Thus, a regular feature of size produced at its LMC limit of size is permitted to vary from true form to the maximum variation allowed by the boundary of perfect form at MMC.

d) In cases where a geometric tolerance is specified to apply at LMC, perfect form at LMC is required.
Rule #2
All applicable geometric tolerances rule. RFS applies, with respect to the individual tolerance, datum reference, or both, where no modifying symbol is specified. MMC or LMC must be specified on the drawing where it is required.
Runout
A composite tolerance used to control the functional relationship of one or more features of a part to a datum axis.
Runout Control
There are two types of runout tolerances: circular runout and total runout.
Scale
The ratio of the object size as drawn to its full size.
Secondary Datum
The second datum plane that the part contacts in a dimensional measurement
Separate Requirement
This tolerance is verified as a separate inspection item. The part must meet this requirement to be accepted.
Shall
Establishes a mandatory requirement.
Should
Used when it is necessary to express nonmandatory provisions.
Simulated Datum
A point, axis, or plane established by processing or inspection equipment, such as the following simulators: a surface plate, a gage surface, or mandrel.<br><br>In industry for practical purposes, the terms "simulated datum" and "datum" are used interchangeably.
Simultaneous Requirement
If two or more features (or patterns of features) are located by basic dimensions relative to common datum features referenced in the same order of precedence and the same material condition, they are considered a single pattern.
Six Degrees of Freedom
Rotation around the X, Y, or Z axis, and movement along the X, Y, or Z axis.
Special-Case Feature of Size Datum
When a feature of size datum feature is referenced at MMC, but simulated in the gage at a boundary other than MMC.
Spotface
Where no depth is specified, a spotface is the minimum depth necessary to clean up the surface to the diameter specified.
Straightness (Axis or Centerplane)
The condition where each line element (or derived median line, or derived median plane) is a straight line.
Straightness of a Line Element
The condition where each line element (or axis or centerplane) is a straight line.
Straightness Control
A geometric tolerance that, when directed to a surface, limits the amount of straightness error allowed in each surface line element. A straightness control is applied in the view where the elements to be controlled are represented by a straight line.
Symmetrical Relationship
Symmetrical relationships may be controlled using position, profile, or symmetry tolerances.
Symmetry
The condition where the median points of all opposed elements of two or more surfaces of a feature of size are congruent with the datum axis or datum center plane of a datum feature.
Symmetry Control
A geometric tolerance that limits the symmetry error of a part feature.
Tangent Plane
A plane that is tangent to the high points of the surface.
Tangent Plane Modifier
The geometric tolerance only applies to the tangent plane of the toleranced surface.
Tertiary Datum
The third datum plane that the part contacts in a dimensional measurement.
Theoretical Datum Feature
The theoretically perfect boundary used to establish a datum from a specified datum feature.
Third Angle Projection
The formation of an image or view upon a plane of projection placed between the object and the observer.
3-2-1 Rule
Defines the minimum number of points of contact required for a part datum feature with its primary, secondary, and tertiary datum planes.
Tolerance
The total amount a specific dimension is permitted to vary. The tolerance is the difference between the maximum and minimum limits.
Tolerance Accumulation
A condition where the tolerances from several dimensions combine to result in a greater amount of tolerance for a part distance.
Tolerance Analysis Chart
A means of graphically displaying the limits of a part as defined by the print specifications
Tolerance of Position Control
A geometric tolerance that defines the location tolerance of a feature of size from its true position.
Tolerance Stack
A calculation that determines the theoretical maximum or minimum distance between two features on a part or in an assembly.
Tolerance Zone
The area (zone) that represents the total amount that part features are permitted to vary from their specified dimension.
Total Runout
The area (zone) that represents the total amount that part features are permitted to vary from their specified dimension.
Total Runout Control
A geometric tolerance that limits the amount of total runout of a surface.
True Geometric Counterpart
The theoretically perfect boundary (virtual condition or actual mating envelope) or best fit (tangent) plane of a specified datum feature.
True Position
The theoretically exact location of a feature of size defined by basic dimensions.
True Profile
A profile defined by basic radii, basic angular dimensions, basic coordinate dimensions, basic size dimensions, undimensioned drawings, formulas, or mathematical data, including design models.
Unequal Bilateral Plus-Minus Tolerance
The allowable variation is from the nominal value, and the variation is not the same in both directions.
Unequal Disposed Profile
Indicates a unilateral or unequally disposed profile tolerance.
Unilateral
In the Direction That Adds Material - A uniform boundary tolerance zone that is offset to the outside of the true profile.
Unilateral
In the Direction That Removes Material - A uniform boundary tolerance zone that is offset to the inside of the true profile.
Unilateral Tolerance Zone
A uniform boundary tolerance zone that is offset to one side of the true profile.
Unrelated Actual Mating Envelope
A similar perfect feature counterpart expanded within an internal feature(s) or contracted about an external feature(s) and not constrained to any datum(s).
Unrelated Actual Mating Envelope
External - A similar perfect feature(s) counterpart of smallest size contracted about an external feature(s) and not constrained to any datum(s).
Unrelated Actual Mating Envelope
Internal - A similar perfect feature(s) counterpart of largest size that can be expanded within an internal feature(s) and not constrained to any datum(s).
Unrelated Actual Minimum Material Envelope
A similar perfect feature counterpart contracted about an internal feature(s) or expanded within an external feature(s) and not constrained to any datum reference frame.
Variable Gaging
Any gaging operation that measures part variation and provides a quantitative value of the variation.
Virtual Condition (VC)
A constant boundary generated by the collective effects of a size feature specified at MMC or LMC material condition and the geometric tolerance for that material condition.
Virtual Condition Boundary Theory
A theoretical virtual condition boundary that limits the location of features of size.
Will
Establishes a declaration of purpose on the part of the design activity.
Worst-case Boundary (WCB)
A general term to refer to the extreme boundary of a feature of size that is the worst case for assembly.
Zero Tolerance at MMC
A method of tolerancing part features that includes the tolerance geometric value with the feature of size tolerance and states a zero at MMC in the feature control frame.