| actual size | (n) A tolerancing measure used to describe the size of a finished part after machining.
(See 504)
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| allowance | (n) A tolerancing measure used to describe the minimum clearance or maximum interference between parts. Allowance is the tightest fit between two mating parts.
(See 504)
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| angularity | (n) An orientation control for geometric dimensioning and tolerancing. Angularity is a condition of a surface, center plane, or axis at an angle other than a right angle to a datum plane or datum axis.
(See 530)
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| arrow plot | (n) A visualization technique in which the dependent variable is a vector rather than a scalar and is represented by line or arrow marks. Because there are typically a large number of arrow marks in a small region, pattern (texture) perception can be used to evaluate trends in the data.
(See 480)
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| basic dimension | (n) A tolerancing measure used to describe the theoretically exact size of a feature.
(See 480)
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| basic size | (n) A tolerancing measure used to describe the theoretical size used as a starting point for the application of tolerances.
(See 507)
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| clearance fit | (n) A tolerancing measure used to describe a fit in which two mating parts always leave a space when assembled. The resulting space is called an allowance or a clearance and is usually specified in the assembly drawings.
(See 504)
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| contour line | (n) A line that represents the inde-pendent variable (X,Y) combinations that result in a constant dependent variable value (also called an isoline). Acontour line can also represent the juncture between two surfaces of differing orientations or depths. In this definition, a contour line is an alternate term for edge.
(See 494)
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| coordinate dimensioning | (n) A technique in which all dimensions are calculated as Cartesian X and Y distances from an origin point, usually located at the lower left-hand corner of the part. Also known as datum dimensioning or baseline dimensioning, coordinate dimensioning should be used cautiously because of the tolerance stackup that takes place.
(See 483)
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| cylindricity | (n) A form control for geometric dimensioning and tolerancing. Cylindricity indicates that all points on the surface should be equidistant from a common axis. Unlike circularity, cylindricity refers to both the circular and the linear (longitudinal) elements on the surface.
(See 530)
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| datum | (n) A theoretically exact point, axis, or plane used as a reference for tabular dimensioning. A datum marks the origin from which the location and orientation of geometric features are established.
(See 523)
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| datum feature | (n) A term used in geometric dimensioning and tolerancing to describe a real or theoretical feature selected to ensure the proper orientation or location of other features on a part. Controls define features on the part relative to the datum features.
(See 526)
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| datum reference frame | (n) Aterm used in geometric dimensioning and tolerancing to describe the theoretical reference frame used to evaluate the location and orientation of features of a part. The frame consists of three mutually perpendicular (orthogonal) planes, which typically correspond to the principal planes of projection in a multiview drawing or the global coordinate system in a 3-D modeling system. In inspections, a physical surface may be established to simulate one of the reference planes.
(See 525)
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| diameter symbol | (n) A symbol used in ANSI dimensioning that precedes a numerical value, indicating that the value shows the diameter of a circle. The symbol used is the Greek letter phi (ø).
(See 482)
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| dimension | (n or v) The physical size of an object, or the process of documenting physical sizes. The number of dimensions used to describe the object depends on whether length (1-D), area (2-D), or volume (3-D) is being measured. Dimensioning can also refer to the measurement of size, location, and orientation of particular features on an object.
(See 480)
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| envelope principle | (n) A term used in geometric dimensioning and tolerancing to describe how much a feature can deviate from ideal form, orientation, or position as it departs from maximum material condition.
(See 523)
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| extension line | (n) Athin, solid line perpendicular to a dimension line, indicating which feature is associated with the dimension.
(See 481)
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| feature control frame | (n) A rectangular outline containing geometric dimensioning and tolerancing information used in the engineering, production, and inspection of a part. The lefthand compartment inside the frame contains the symbol of the geometric control being applied. The middle compartment contains the size of the tolerance zone. The right-hand compartment contains the datum identification symbol(s).
(See 520)
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| functional analysis and design | (n) A design driven by the intended use of the product. Functional analysis determines if the design is an answer to the problem statement written during the ideation phase. Aesthetic considerations are often considered the foil to functional consider-ations.
(See 506)
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| fundamental deviation | (n) A tolerancing measure used to describe the deviation closest to the basic size.
(See 510)
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| geometric dimension | (n) A dimension that specifies the size and location of a feature, as well as other geometric qualities such as form and orientation. Geometric dimensioning and tolerancing, combined with statistical process control, provide a robust approach to inspection
other elements in a drawing or sketch.
system, or geometric primitives in a CAD and quality control for manufactured parts.
(See 478)
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| hole basis | (n) A tolerancing measure used to describe a system of fits in which the minimum hole size is the basic size.
(See 510)
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| interference fit | (n) A fit in which two toleranced mating parts will always interfere when assembled because the “male” part is larger than the “female” part. The resulting difference in sizes, also called the allowance, means that force is required to assemble the part. An interference fit fixes or anchors the two parts as if they were one.
(See 504)
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| international tolerance grade | (n) A group of tolerances that vary depending on basic size but have the same level of accuracy with a given grade. The smaller the grade number, the smaller the tolerance zone.
(See 510)
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| leader line | (n) Athin, solid line used to indicate the feature with which a dimension, note, or symbol is associated. Leader lines are terminated at one end with an arrow touching the part or detail and a short horizontal shoulder on the other end. Text is extended from the shoulder of the leader.
(See 482)
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| least material condition (LMC) | (n) A tolerancing term indicating the condition of a part when it contains the least amount of material possible. The LMC of an external feature is the lower limit of the part. The LMC of an internal feature is the upper limit of the part.
(See 522)
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| limits | (n) The maximum and minimum sizes shown by the toleranced dimension. The larger value in a toleranced dimension is called the upper limit and the smaller value is the lower limit.
(See 504)
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| lower deviation | (n) Atolerancing term describing the difference between the minimum size limit and the basic size.
(See 507)
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| maximum material condition (MMC) | A tolerancing term defining the condition of a part when it contains the most amount of material. The MMC of an external feature, such as a shaft, is the upper limit. The MMC of an internal feature, such as a hole, is the upper limit. The MMC of an internal feature, such as a hole, is the lower limit.
(See 522)
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| nominal size | (n) A dimension used to describe the general size of an object, usually expressed in common fractions. For example, a bolt might have a nominal size of 1/2′.
(See 504)
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| parallelism | (n) An orientation control for geometric dimensioning and tolerancing. Parallelism is a condition in which a surface or an axis is equidistant at all points from a datum plane or datum axis, respectively. The distance between the feature and the datum is the tolerance value given in the control frame.
(See 530)
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| perpendicularity | (adj.) An orientation control for geometric dimensioning and tolerancing. Perpendicularity is the condition of a surface, center plane, or axis that is at a right angle to a datum plane or datum axis, respectively.
(See 530)
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| plus and minus dimensioning | (n) A tolerancing specification that gives the allowable positive and negative variance from the dimension specified. Sometimes, the plus and minus values will be equal; at other times, they will be different.
(See 482)
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| position | (n) Acontrol for geometric dimensioning and tolerancing. Position specifies the total zone specification for a feature, such as a diameter or the total height.
(See 534)
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| profile | (n) A form control for geometric dimensioning and tolerancing. A profile is the outline of a feature projected onto a plane. They usually consist of combinations of contiguous lines, arcs, and other curves. The profile tolerance zone may be made of a combination of straightness, roundness, parallelism, etc.
(See 531)
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| radius symbol | (n) A symbol that precedes a numerical value, indicating that the associated dimension shows the radius of a circular arc. The radius symbol is the capital letter R.
(See 482)
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| reference dimension | (n) A numerical value, enclosed in parentheses, provided for information only and not used in the fabrication of the part. A reference dimension is a calculated size used to show the intended design size of a part. Drawings made to older standards may use REF placed next to a reference dimension, instead of using parentheses.
(See 480)
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| runout | (n) A filleted surface that runs tangent to a cylindrical one. Arunout is drawn on multiview drawings starting at the point of tangency, using a radius equal to that of the filleted surface, with a curvature of approximately one-eighth of a circle.
(See 534)
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| shaft basis | (n) A tolerancing technique used to define a system of fits and based on the basic size as being the maximum size of the shaft.
(See 510)
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| statistical process control | (n) The system used for the selection of parts that are then measured for accuracy. Mathematical statistics is the tool used to analyze the measurements of the randomly selected parts. Consistent and accurate measurements will indicate when a machine tool must be maintained or adjusted during the manufacturing cycle.
(See 519)
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| system | (n) An orderly arrangement of parts that are combined to serve the same general function. Examples are the arrangement of the assembly process in a factory; the heating, ventilating, and air conditioning (HVAC) system in a structure; and the electrical system in an automobile.
(See 504)
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| tolerance | (n) The difference between the maximum and minimum size limits on a part. Tolerancing is a fundamental technique in precision manufacturing applications.
(See 504)
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| tolerance zone | (n) A tolerance term that represents the tolerance and its position in relation to the basic size.
(See 510)
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| transition fit | (n) A fit that occurs when two toleranced mating parts will sometimes be an interference fit and sometimes be a clearance fit when assembled. Both the loosest and tightest fits for any two mating parts must be calculated, often using tables associated with standard parts.
(See 505)
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| unidirectional dimensioning | (n) A style of dimensioning in which the dimension and note text are oriented to be read from the bottom of the drawing, relative to the drawing format. This is an ANSI approved style of dimensioning.
(See 487)
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| upper deviation | (n) A tolerancing term describing the difference between the maximum size limit and the basic size.
(See 507)
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2002 McGraw-Hill Higher Education