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Dimensioning and Tolerancing

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1 Dimensioning and Tolerancing
CHAPTER 10 Dimensioning and Tolerancing

2 Learning Objectives Identify and use common dimensioning systems
Explain and apply dimensioning standards based on ASME Y Apply proper specific notes for manufacturing features Place proper general notes and flag notes on a drawing Interpret and use correct tolerancing techniques

3 Learning Objectives Prepare completely dimensioned multiview drawings from engineering sketches and industrial drawings Apply draft angles as needed to a drawing Dimension CAD/CAM machine tool drawings Prepare casting and forging drawings

4 Learning Objectives Provide surface finish symbols on drawings
Solve tolerance problems including limits and fits Use an engineering problem as the basis for your layout techniques Describe the purpose of ISO 9000 Quality Systems Standard and related standards

5 Dimensions Required on detail drawings
Provide shape and size description Size dimensions Location dimensions Notes Local notes (specific notes) General notes

6 Dimensions

7 ASME Dimensioning Standards
ASME Y14.5, Dimensioning and Tolerancing General note: DIMENSIONING AND TOLERANCING PER ASME Y Several other ASME documents with standards related to dimensioning and tolerancing

8 Dimensioning Definitions
Actual size Feature of size Allowance Geometric tolerance Basic dimension Least material condition (LMC) Bilateral tolerance Datum Limits of dimension Diameter Feature

9 Dimensioning Definitions
Maximum material condition (MMC) Specified dimension Nominal size Tolerance Radius Unilateral tolerance Reference dimension Stock size

10 Fundamental ASME Y14.5 Dimensioning Rules
Each dimension has a tolerance except reference, maximum, minimum, or stock Dimensioning and tolerancing must be complete Show each necessary dimension of an end product Select and arrange dimensions to suit the function and mating relationship of a part

11 Fundamental ASME Y14.5 Dimensioning Rules
Dimensions must not be subject to more than one interpretation Do not specify the manufacturing processes unless necessary Identify nonmandatory dimensions with an appropriate note Arrange dimensions to provide required information and optimum readability Show dimensions in true profile views and visible outlines

12 Fundamental ASME Y14.5 Dimensioning Rules
Dimension diameter or thickness of materials manufactured to gage or code numbers 90°angle is implied for centerlines and lines 90°basic angle is implied for centerlines located by basic dimensions A zero basic dimension applies where axes, center planes, or surfaces are shown one over the other with established geometric controls

13 Fundamental ASME Y14.5 Dimensioning Rules
Unless otherwise specified, all: Dimensions and tolerances are measured at 20°C (68°F) Dimensions and tolerances apply in a free state condition except for nonrigid parts Tolerances apply for the full depth, length, and width of the feature Dimensions and tolerances apply on the drawing where specified

14 Fundamental ASME Y14.5 Dimensioning Rules
Coordinate systems: Right-handed (arranged clockwise) Labeled axes and positive direction shown 3-D model complies with ASME Y14.41, Digital Product Definition Data Practices

15 Dimensioning Components

16 Dimensioning Symbols

17 Unidirectional Dimensioning
Numerals, figures, and notes lettered horizontally Read from the bottom of the drawing sheet Mechanical drafting for manufacturing

18 Aligned Dimensioning Numerals, figures, and notes aligned with the dimension lines Architectural and structural drafting Horizontal dimensions read from the bottom Vertical dimensions read from the right side

19 Rectangular Coordinate Dimensioning without Dimension Lines
Dimension values aligned with extension lines Dimension represents a measurement originating from datums or coordinates Features such as holes sized using specific notes or a table Popular for: Precision sheet metal part drawings Electronics drafting

20 Rectangular Coordinate Dimensioning without Dimension Lines

21 Tabular Dimensioning Form of rectangular coordinate dimensioning without dimension lines Features dimensioned in a table

22 Chart Dimensioning Used when a part or assembly has one or more dimensions that change depending on the specific application

23 Millimeter Dimensions
Millimeters (mm) Common International System of Units (SI) unit of measure General note: UNLESS OTHERWISE SPECIFIED, ALL DIMENSIONS ARE IN MILLIMETERS Follow any inch dimensions with IN

24 Proper Use of Metric Units
Omit decimal point and 0 when dimension is a whole number Precede a decimal value that is less than 1 with a 0 When the value is greater than a whole number by a fraction of a mm, do not place a 0 next to last digit Exception: when displaying tolerance values

25 Proper Use of Metric Units
Plus and minus tolerance values have same number of decimal places Limit tolerance values have same number of decimal points Unilateral tolerances use a single 0 without a corresponding + or – sign

26 Inch Dimensions Decimal inches (IN)
United States (U.S.) customary unit of measure General note: UNLESS OTHERWISE SPECIFIED, ALL DIMENSIONS ARE IN INCHES Follow any millimeter dimensions with mm

27 Proper Use of Inch Units
Do not precede a value that is less than 1 inch with a 0 Express a specified dimension to the same number of decimal places as its tolerance Fractional inches generally indicate larger tolerance

28 Proper Use of Inch Units
Plus and minus tolerance values have the same number of decimal places Unilateral tolerances use the + and – sign The 0 value has the same number of decimal places as the value that is greater or less than 0 Limit tolerance values have the same number of decimal points

29 Proper Use of Angular Units
Use decimal or degrees–minutes–seconds format Angle and tolerance values have the same number of decimal places Include 0°or 0°0″ when specifying only minutes or seconds, as applicable

30 Using Fractions Not as common as decimal inches or millimeters
Architectural and structural drawings Generally indicate larger tolerance

31 Arrowheads Terminate dimension lines and leaders
Three times as long as they are wide Consistent size Filled in solid or open

32 Dimension Line Spacing
First dimension line: Uniform distance from the object .375 in. (10 mm) minimum in. ( mm) preferred Succeeding dimension lines: Equally spaced .25 in. (6 mm) minimum in. ( mm) preferred

33 Dimension Numerals

34 Chain Dimensioning Creates tolerance stacking (tolerance buildup)
Omit one intermediate dimension or the overall dimension

35 Baseline Dimensioning
Size or location of features controlled from a common reference plane Reduces possibility of tolerance stacking

36 Direct Dimensioning Results in the least tolerance stacking

37 Dimensioning Symmetrical Objects

38 Dimensioning Cylinders

39 Dimensioning Square Features

40 Preferred Dimensioning Practices
Avoid crossing extension lines Do not break extension lines when they cross Never cross extension lines over dimension lines Break the extension line where it crosses over a dimension line when necessary

41 Preferred Dimensioning Practices
Never break a dimension line Break extension lines when they cross over or near an arrowhead Avoid dimensioning over or through the object Avoid dimensioning to hidden features

42 Preferred Dimensioning Practices
Avoid long extension lines Avoid using any line of the object as an extension line Dimension between views when possible Group adjacent dimensions

43 Preferred Dimensioning Practices
Dimension to views that provide the best shape description Do not use a centerline, extension line, phantom line, visible object line, or a continuation of any of these lines as a dimension line Stagger adjacent dimension numerals so they do not line up

44 Dimensioning Angular Surfaces

45 Dimensioning Chamfers

46 Dimensioning Conical Shapes

47 Dimensioning Hexagons and Other Polygons
Dimension across the flats

48 Dimensioning Arc Radius

49 Dimensioning Arc Length

50 Additional Radius Dimensioning Applications
True radius TRUE R followed by the actual radius Controlled radius CR followed by the radius Spherical radius SR followed by the radius

51 Dimensioning Contours Not Defined as Arcs
Dimension coordinates or points along the contour from common surfaces Series of dimensions on the object and along the contour Tabular dimensioning

52 Locating a Point Established by Extension Lines

53 Dimensioning Circles and Thru Holes

54 Dimensioning Blind Holes

55 Dimensioning a Counterbore

56 Dimensioning a Spotface

57 Countersink or Counterdrill

58 Dimensioning Multiple Features
Number of features, X, a space, feature specification Dimension to one of the features only Examples: 4X Ø6 THRU or 4X Ø6 2X R.50 3X 8X45°

59 Dimensioning Slots

60 Dimensioning Keyseats and Keyways

61 Dimensioning Knurls

62 Dimensioning Necks and Grooves

63 Rectangular Coordinate Dimensioning

64 Polar Coordinate Dimensioning

65 Dimensioning Repetitive Features

66 Locating Multiple Tabs in a Polar Orientation

67 Locating Multiple Features of Nearly the Same Size

68 Specifying Dimension Origin
Clearly identifies from which feature the dimension originates

69 Dimensioning Auxiliary Views

70 General Notes and Specifications
Sheet blocks: Outside sheet blocks: Material Machining practices General tolerances Common dimensions Scale Finish or other treatments Part name Sheet size Part number Number of revisions Projection

71 Flag Notes Delta note Specific note placed with general notes
Keyed to the drawing Delta symbol (Δ) common Hexagons and circles also used

72 Tolerances Help ensure parts fit together and function in an assembly
Apply to all dimensions on a drawing, except: Reference Maximum Minimum Stock size

73 Plus-Minus Dimensioning
Calculate the upper and lower limits from the specified dimension and plus-minus tolerance Bilateral tolerance Most common tolerancing method Equal bilateral tolerance [Insert 6.5  0.2, match to unequal bilateral tolerance style] Often preferred by manufactures Unequal bilateral tolerance [Insert ]

74 [Insert , match to unequal bilateral tolerance style]
Unilateral Tolerance [Insert , match to unequal bilateral tolerance style] Used by some companies to define fits between mating parts Often avoided by CNC machine programmers

75 Limit Dimensioning Calculate the tolerance from the upper and lower limits Common for defining fits between mating parts Preferred by some companies or departments

76 Single Limits Can be used for common machine processes
Follow dimension value with (MIN) or (MAX) Design determines unspecified limit

77 Specified and Unspecified Inch Tolerances

78 Specified and Unspecified Metric Tolerances
ISO 2768 classes of size tolerances: Fine (f) Medium (m) Coarse (c) Very coarse (v)

79 Applying Statistical Tolerancing

80 Maximum Material Condition (MMC)
External feature is at MMC at its largest limit Internal feature is at MMC at its smallest limit

81 Least Material Condition (LMC)
External feature is at LMC at its smallest limit Internal feature is at LMC at its largest limit

82 Clearance Fit

83 Allowance MMC Internal Feature – MMC External Feature Allowance

84 Interference Fit Force or shrink fit Examples:
Bushing pressed onto a housing Pin is pressed into a hole

85 Extreme Form Variation
Established by limits of size Specified by “Rule 1” in ASME Y14.5

86 Limits and Fits Between Mating Parts
Fit determined first based on the use or service Limits of size established second to ensure the desired fit ANSI/ASME B4.1 Preferred Limits and Fits for Cylindrical Parts ANSI/ASME B4.2 Preferred Metric Limits and Fits Tables of establishing dimensions for standard ANSI fits

87 Running and Sliding Fits (RFC)
RC1—Close sliding fits RC2—Sliding fits RC3—Precision running fits RC4—Close running fits RC5 and RC6—Medium running fits RC7—Free running fits RC8 and RC9—Loose running fits

88 Locational Fits (LC, LT, LN)
LC—Locational clearance fits LT—Locational transition fits LN—Locational interference fits

89 Force Fits (FN) FN1—Light drive fits FN2—Medium drive fits
FN3—Heavy drive fits FN4 and FN5—Force fits

90 Dimensions Applied to Platings and Coatings
General note: DIMENSIONAL LIMITS APPLY BEFORE (AFTER) PLATING (COATING) Specific note: Leader with a dot pointing to the specific surface instead of an arrowhead

91 Casting Drawing and Design
Depends on: Casting process and characteristics Material Design or shape of the part Die or mold Based on ASME Y14.8, Castings and Forgings standard

92 Shrinkage Allowance Extra material to account for cooling Examples:
Iron .125 in. per ft. (.4 mm per meter) Steel .250 in. per ft. Aluminum .125 to .156 in. per ft. (.4 mm–.5 per meter) Brass .22 in. per ft. (.7 mm per meter) Bronze .156 in. per ft. (.5 mm per meter) Patternmaker applies shrink rules

93 Draft Not necessary on horizontal surfaces
Begin at the parting line and parting plane Tapers away from the molding material

94 Draft on a Drawing General note: Angular dimensions
ALL DRAFT ANGLES .010 ALL DRAFT ANGLES 6° Angular dimensions Plus draft and/or minus draft methods

95 Parting Lines on a Drawing

96 Fillets and Rounds in Casting
Allow the pattern to eject freely from the mold Fillets help reduce the tendency of cracks to develop during shrinkage Radii determined by part thickness

97 Machining Allowance Extra material for any surface to be machined
Examples: Iron and steel .125 in. (3 mm) Brass, bronze, and aluminum .062 in. (1.5 mm) Greater for large castings or those with a tendency to warp

98 Casting Drawings Casting drawing Machining drawing
Combined casting and machining drawing Drawing phantom lines to show machining allowance and draft angles

99 Forging Design and Drawing
Focuses on dies Draft Fillets and rounds Machining allowance Based on ASME Y14.8, Castings and Forgings standard

100 Forging Drawings Stock material drawings: Detail drawings
Show size and shape of the stock material Outline of the end product using phantom lines Detail drawings Show the end product Usually show draft Use phantom lines to show machining allowance and draft angles

101 Surface Finish (Surface Texture)
Obtained by: Machining Grinding Honing Lapping Specified using surface finish symbol

102 Surface Finish Characteristics
Roughness Waviness Lay Flaws

103 Surface Finish Symbol

104 Design and Drafting of Machined Features
Capabilities of the machinery available Least-expensive method to get the desired result Avoid over-machining

105 Tool Design Jig and fixture design
Machining operations require special tools to hold the workpiece or guide the machine tool Involves knowledge of: Kinematics Machining operations Machine tool function Material handling Material characteristics

106 Jig and Fixture Drawings
Assembly drawing with all components of the tool Fast-acting clamps Spring-loaded positioners Clamp straps Quick-release locating pins Handles Knobs

107 Jig and Fixture Drawings

108 Tools in Manufacturing
Drill jigs Datums Drill fixtures Machining fixtures Welding fixtures Inspection fixtures Progressive dies

109 Qualities of Tools Reliability Repeatability Ease of use
Ease of manufacture Ease of maintenance and repair

110 Basic Elements of Tool Design
Visualizing how shop personnel will accomplish a specific task Conceptualizing hardware to assist in the accomplishment of that task Creating drawings so the hardware can be manufactured

111 Introduction to ISO 9000 ISO 9000-1 ISO 9001 ISO 9002
Direction and definitions that describe what each standard contains Assists companies in the selection and use of the appropriate ISO standard ISO 9001 Model for designing, documenting, and implementing ISO standards ISO 9002 ISO 9001 but does not contain the requirement of documenting the design and development process

112 Introduction to ISO 9000 ISO 9003 ISO 9004-1
Companies or organizations that only need to demonstrate through inspection and testing methods that they are providing the desired product or service ISO Set of guidelines for development and implementation of a quality management system

113 Glossary Actual size Allowance
The measured size of a feature or part after manufacturing. Allowance The tightest possible fit between two mating parts.

114 Glossary Baseline dimensioning Basic dimension Bilateral tolerance
A common method of dimensioning machine parts whereby each feature dimension originates from a common surface, axis, or center plane. Basic dimension A theoretically exact size, location, profile, or orientation of a feature or point. Bilateral tolerance A tolerance allowed to vary in two directions from the specified dimension.

115 Glossary Bilateral tolerance Blind hole Casting
A tolerance in which variation is permitted in both directions from the specified dimension. Blind hole A hole that does not go through. Casting An object or part produced by pouring molten metal into a mold.

116 Glossary Chain dimensioning Chamfer Clearance fit
Also known as point-to-point dimensioning, a method of dimensioning from one feature to the next. Chamfer A slight surface angle used to relieve a sharp corner. Clearance fit A condition when, due to the limits of dimensions, there is always a clearance between mating parts.

117 Glossary Controlled radius Counterbore Counterdrill
The limits of the radius tolerance zone must be tangent to the adjacent surfaces, and there can be no reversals in the contour. Counterbore Often used to machine a diameter below the surface of a part so a bolt head or other fastener can be recessed. Counterdrill A combination of two drilled features.

118 Glossary Countersink Datum Delta
A conical feature in the end of a machined hole. Datum A theoretically exact surface, plane, axis, center plane, or point from which dimensions for related features are established. Delta A triangle symbol (Δ) placed on the drawing for reference.

119 Glossary Diameter Die Dimension
The distance across a circle measured through the center. Die Any device used to produce a desired shape, form or finish to a material. Dimension A numerical value or values, or mathematical expression provided in appropriate units of measure and used to define form, size, orientation or location of a feature or part.

120 Glossary Direct dimensioning Draft Equal bilateral tolerance
Dimensioning applied to control the size or location of one or more specific features. Draft The taper allowance on all vertical surfaces of a pattern, which is necessary to facilitate the removal of the pattern from the mold. Equal bilateral tolerance A tolerance where the variation from the specified dimension is the same in both the + and – directions.

121 Glossary Extreme form variation Feature of size Feature
The variation of the form of the feature between the upper limit and lower limit of a size dimension. Feature of size One cylindrical or spherical surface, a circular element, or a set of two opposed elements or opposed parallel plane surfaces, each of which is associated with a directly toleranced dimension. Feature The general term applied to describe a physical portion of a part or object, such as a surface, slot, tab, pin, keyseat, or hole.

122 Glossary Forging Free state condition General notes
A process of shaping malleable metals by hammering or pressing between dies that duplicate the desired shape. Free state condition Distortion of the part after removal of forces applied during manufacturing. General notes Information that relates to the entire drawing.

123 Glossary General notes Geometric tolerance Interference fit
Notes placed separate from the views and relate to the entire drawing. Geometric tolerance The general term applied to the category of tolerances used to control size, form, profile, orientation, location, and runout. Interference fit The condition that exists when, due to the limits of the dimensions, mating parts must be pressed together.

124 Glossary Keyseat Keyway Kinematics A groove or channel cut in a shaft.
A shaft and key are inserted into a hub, wheel, or pulley where the key mates with a groove called a keyway. Kinematics The study of mechanisms.

125 Glossary Knurling Lay Least material condition (LMC)
A cold forming process used to form a cylindrical or flat surface uniformly with a diamond or straight pattern creating a knurl. Lay The direction or configuration of the predominant surface pattern. Least material condition (LMC) The condition where a feature contains the least amount of material allowed by the size limits.

126 Glossary Least material condition (LMC) Limit dimensioning
The opposite of MMC, the least amount of material possible in the size of a feature within the stated limits. Limit dimensioning A system of dimensioning where the upper and lower limits of the tolerance are provided and there is no specified dimension given. Limits of dimension The largest and smallest possible boundary to which a feature can be made as related to the tolerance of the dimension.

127 Glossary Limits of size Local notes (specific notes)
The amount of variation in size and geometric form of a feature control. The boundary between maximum material condition (MMC) and least material condition (LMC). Local notes (specific notes) Notes connected to specific features on the views of the drawing. Location dimensions Dimensions that provide the relationship of features of an object.

128 Glossary Locational fits (LC, LT, LN) Maximum material condition (MMC)
Provide rigid or accurate location, as with interference fits, or provide some freedom of location, as with clearance fits. Maximum material condition (MMC) The condition of a part or feature when it contains the most amount of material within the stated limits.

129 Glossary Mold Neck Nominal size
A form made to pour or inject material to produce the desired shape. Neck The result of a machining operation that establishes a narrow groove on a cylindrical part or object. Nominal size A dimension used for general identification such as stock size or thread diameter.

130 Glossary Nonrigid parts Notes Parting line
Parts that can have dimensional change due to thin wall characteristics. Notes A type of dimension that generally identify the size of a feature or features with written specifications that are more detailed than a numerical value. Parting line The separation between the mold or die components, and is a line on the drawing representing the mating surfaces between the mold or die components.

131 Glossary Parting plane Patternmaker Plus-minus dimensioning
The mating surfaces of a die or mold. Patternmaker A person who makes a pattern for casting and forging applications. Plus-minus dimensioning A system of dimensioning that provides a nominal dimension and an amount of allowable variance from that dimension.

132 Glossary Polar coordinate dimensioning Radius
Using angular dimensions to locate features from planes or centerlines. Radius The distance from the center of a circle to the outside. Rectangular coordinate dimensioning Using linear dimensions to locate features from planes or centerlines.

133 Glossary Reference dimension Running and sliding fits (RFC)
A dimension used for information purposes only and is usually without a tolerance. Running and sliding fits (RFC) Intended to provide a similar running performance with suitable lubrication allowance throughout their range of sizes. Single limits Used when the specified dimension cannot be any more than the maximum or less than the minimum given value.

134 Glossary Size dimensions Specifications Specified dimension
Dimensions placed directly on a feature to identify a specific size or may be connected to a feature in the form of a note. Specifications Any written information or instructions included on the drawing or with a set of drawings, giving all necessary information not shown in the drawing field. Specified dimension The part of the dimension from which the limits are calculated.

135 Glossary Spotface Statistical tolerancing Stock size
Provides a flat bearing surface for a washer face or bolt head. Statistical tolerancing The assigning of tolerances to related dimensions in an assembly based on the requirements of statistical process control (SPC). Stock size A commercial or pre-manufactured size, such as a particular size of square, round, or hex steel bar.

136 Glossary Surface finish (surface texture) Surface roughness
The roughness, waviness, lay, and flaws of a surface. Surface roughness Fine irregularities in the surface finish and is a result of the manufacturing process used. Surface waviness The often widely spaced condition of surface texture usually caused by such factors as machine chatter, vibrations, work deflection, warpage, or heat treatment

137 Glossary Tolerance stacking (tolerance buildup) Tolerance True radius
The tolerance of each dimension builds on the next. Tolerance The total permissible variation in size or location. True radius The actual radius of an arc even though it may be shown not true size and shape.

138 Glossary Unequal bilateral tolerance Unilateral tolerance
A tolerance where the variation from the specified dimension is not the same in both directions. Unilateral tolerance A tolerance where the variation is permitted to increase or decrease in only one direction from the specified dimension.

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