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Dimensioning Methods Dimensioning and Tolerancing Dimensioning Methods Dimensioning of Features
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Page 1: Dimensioning Module

Dimensioning Methods

Dimensioning and Tolerancing

Dimensioning Methods

Dimensioning of Features

Page 2: Dimensioning Module

Dimensioning and Tolerancing

DIMENSIONING AND TOLERANCING GENERAL RULES:

DEFINITIONS

FUNDAMENTAL RULES

UNITS OF MEASURE

DIMENSIONS AND TOLERANCES

Page 3: Dimensioning Module

DefinitionsDimension.A numerical value expressed in appropriate units of measure and indicated on a drawing/model along with lines, symbols, and notes to define the geometrical characteristic of an object.

Basic DimensionA numerical value used to describe the theoretically exact size, shape, or location of a feature or datum target.It is the basis from which permissible variations are established by tolerances onother dimensions, in notes, or in feature control frames.Single Limit Dimension.A dimension followed by the term MIN or MAX to provide a single limit.Unless limited by other dimensions, the other limit for a minimum dimension is infinity and for a maximum dimension is zero.Reference Dimension.

A dimension, usually without tolerance, used for information purposes only.

It does not govern production or inspection operations.A reference dimension is derived from other values shown on the drawing/model or on related drawings/models.

Page 4: Dimensioning Module

DefinitionsGage Dimension.

A dimension without tolerance used to establish a gauging point, line, diameter, or plane.

Nominal Size.

Actual Size.

The designation used for the purpose of general identification.

The measured size.

Limits of Size. The applicable maximum and minimum sizes.

Tolerance. The total amount by which a specific dimensions is permitted to vary.

The tolerance is the difference between the maximum and minimum limits.

Bilateral Tolerance.A tolerance in which variation is permitted in both directions from the Specified dimension.

Equal bilateral tolerancing is the preferred method.The tolerance may be equal or unequal in both directions.

Unilateral Tolerance.A tolerance in which variation is permitted in one direction from the specified dimension.

Limit Dimensions.A dimensioning method in which a dimension is expressed as the range between a maximum and a minimum value. The tolerance is the difference between the maximum and minimum limits.

Page 5: Dimensioning Module

Fundamental RulesA important part of a drawing/model is the dimensions and tolerances which must clearly and accurately define the size or condition of each feature or characteristic of the component in order to fulfill the design intent.

Dimensioning shall conform to the following rules.All dimensions shall be decimal dimensions except for inch thread designations (fractional dimensions).

Each dimension shall have a tolerance either applied directly, in a general note, by a geometric tolerance, in a specification or in a related document referenced on the drawing/model.Exceptions are dimensions specifically identified as reference ( ) and gage.

Tolerances shown in 1E0011 specification have been added to cover untoleranced dimensions that are shown on many existing drawings.On new and revised drawings/models, tolerances must be specified on the drawing/model for chamfers, hole locations, keyslot locations, and "tool drag” control.

Page 6: Dimensioning Module

Dimensions and tolerances for size, form, and location shall be provided to the extent that there is full definition of the characteristics of each feature.

Fundamental Rules

A feature should not be dimensioned more than once except in certain special cases where an additional dimension is necessary for reference. In these cases, they must be identified as reference ( ) according to Standard B2.2. Neither scaling (measurement of size of a feature directly from a drawing) nor assumption of a distance or size is permitted.

Dimensions shall be: Selected to provide all required information so that every feature of the component can be accurately produced and inspected.Shown in true profile views and refer to visible outlines.

Shown between points, lines, or surfaces having a necessary and specific relationship to each other or controlling the location of other components.Selected and arranged to avoid accumulation of tolerances, suit the function and mating relationship of a part and avoid more than one interpretation.

Surfaces or centerlines shown on drawings/models at right angles to each other are implied to be 90 apart, without specifying the 90 on the drawing/model.

Dimensions and tolerances apply to the completed component in the free state condition, unless otherwise specified.

Page 7: Dimensioning Module

Fundamental RulesProcessing Information.

The drawing/ model should, if possible, define a component without specifying manufacturing methods or processing dimensions.

For example, only the diameter of a hole is given without indication as to whether it may be drilled, reamed, punched, or made by any other process. When design control must specify processing to ensure that the completed component meets design requirements, the drawing/model must include the necessary processing information.

Typical processes and processing dimensions that must be specified by design control are as follows:

a. Dimensions that control procurement of un-machined castings and forgings.

b. Depth of process holes such as drill before ream. Refer to Standard J5.3 for method of specifying process hole depth.

c. Dimensions controlling stock removal to ensure heat-treat case depth or to eliminatesurface defects,seams, or stringers. Refer to Standards H5.15 and H5.16.

d. Sequence of manufacturing operations such as ROLL THREADS AFTER HEAT TREAT.

e. Special processing dimensions in accordance with Standard B2.5 that are enclosed in <>.

f. Processes such as heat treatment, welding, shot-peening, honing, etc. required to fulfilldesign requirements.

g. Process datum systems (designated X, Y, Z) used on welded assemblies and theirindividual parts. See Standard B6.2.

Page 8: Dimensioning Module

Fundamental Rules

When design control need not specify intermediate stages of manufacture to ensure that the completed component meets design requirements, exclude processing dimensions from the drawing/model.

Typical processing dimensions that are not required on drawings/ models are as follows:

Drill diameter before ream, bore, or broach, refer to Standard J5.3 for control of depth of process holes.

Grind dimensions before plating.

Intermediate rough turning, boring, or grinding dimensions.

Page 9: Dimensioning Module

Fundamental RulesRequirement priority (including tolerances) has been established in specification 1E0011 as follows:

Final requirements apply in the order listed: First Priority

Requirements shown on the drawing/model including notes (title block tolerances excluded).Any tolerance may be temporarily overridden by deviation or by special conditions covered in a specification or notice.

Second Priority - Requirements included in applicable specifications.1E specifications, except 1E0011, listed in the specification, material, and heat treatment blocks, including specifications listed as part of another specification.

Tolerances on raw stock are governed by mill tolerance specifications such as 1E2177- Steel Products, 1E2315- Stainless Steel/Heat Resistant Alloys, 1E2324- Aluminum, and 1E2325 – Copper Base Alloys or by applicable society or commercial specifications such as AISI, JIS, BS, DIN, SAE, and ASTM.

Stock dimensions are indicated on drawings/ models:1. By the term 1E____ TOL2. As dimensions associated with CFS or HFS surface texture designations.3. As dimensions that specify material shape identical to material size

Shown in the material block.

Third priority. Requirements included in 1E0011 specification.

Fourth Priority. General tolerances listed in the title block.

Page 10: Dimensioning Module

Units of MeasureThe units of measure to be used on drawings/models are the SI units and their multiples and submultiples.

Most commonly used SI units are : See Standard B0.3 for a complete description of SI

a. Linear - Use mm (millimeters) 1 mm = 0.03937 inch 1 inch = 25.4 mm exactly

b. Surface Texture (Type 1) - Use mm (micrometers) for roughness average. (See Standard B2.4 for standard values).

c. Pressure - Use kpa (kilopascal)1 kPa = 10³ Pa or 0.001 N/mm‚ 1 kPa = 0.1450 psi 1 psi = 6.895 kPa

d. Stress - Use MPa (megapascal) 1 MPa = 10⁶ Pa or 1 N/mm²‚ 1 MPa = 145.0 psi 1 psi = 0.006895 MPa

e. Mass - Use kg (kilograms) or g (grams) 1kg = 2.205 lb 1 lb = 0.4536 kg 1 g = 0.03527 oz 1 oz = 28.35 g

Page 11: Dimensioning Module

Units of Measure f. Force - Use N (newtons) or kN (kilonewtons)

1 N = 0.2248 lb (force) 1 lb (force)=4.448 N1 kN = 224.8 lb (force) 1 lb (force) = 0.004448 kN

i. Temperature - Use degrees Celsius (C) C temp = (F - 32) divided by 1.8 C tol = F tol divided by 1.8 F temp = (C x 1.8+ 32) F tol = C tol x 1.8

g. Torque - Use Newton meters (N-m) 1 N m = 0.7376 lb ft 1 lb ft = 1.356 N m1 N m = 8.851 lb in. 1 lb in. = 0.1130 N m

h. Volume - Use m³(cubic meters), L (liters), mL (milliliters), or cm³cubic centimeters).1 m³= 1.308 yd³ 1 yd³ = 0.7646 m³1 m³= 35.31 ft³ 1 ft³ = 0.02832 m³1 L = 0.03531 ft³ 1 ft³ = 28.32 L1 L = 0.2642 gal. 1 gal. = 3.785 L1 L = 1.056 qt 1 qt = 0.9463 L1 mL = 0.06102 in.³ 1 in.³= 16.39 mL1 mL = 0.03381 oz (fluid) 1 oz (fluid) = 29.57mL

j. Angles - Use degrees----- with partial degrees-expressed decimally.

Preferred increments are whole, half, quarter, and tenths of a degree. For angles determined by calculation, round off and specify to four decimal places. Trailing zeros should be omitted.

Page 12: Dimensioning Module

Dimensions and Tolerances Commas and Spaces.

All digits to the right or left of a decimal point shall be written continuous without any grouping by commas or spaces. This will prevent misinterpretation of a comma as a decimal or a space as an omission resulting from poor reproduction.

Specify as: 2476231 ____not 2,476,231 or 2 476 231.

Millimeter Dimensioning. The following apply where specifying millimeter dimensions:

a. Values less than one.Place a zero before the decimal point on all values of any unit less than one.

Example: 0.2.

b. Whole number values.Where a dimension is a whole number, neither the decimal point nor a zero is shown.

c. Whole number plus decimal values.Where the dimension exceeds a whole number by a decimal portion of one millimeter, the last digit to the right of the decimal point is not followed by a zero.

Page 13: Dimensioning Module

Dimensions and TolerancesDimensions on computer drawings should be rounded for proper display and to reflect the precision of the database geometry from which they were derived (database geometry may be expressed to several decimal places and may be the result of manipulations and calculations used during creation).

Rounding of dimensions and the number of decimal places displayed shall be dependent on the amount of total size tolerance applied to the dimension.

Use the Figure below to round dimensions for display.When it is used, the round off deviation (difference between displayed dimension and database geometry) will be less than 5% of the total tolerance applied to the dimension

Decimal Place Requirements for Dimensions

Page 14: Dimensioning Module

Dimensions and TolerancesNon-millimeter Units

Specification of non-millimeter units seldom requires use of decimal parts of a unit. Preferred increments of 10, 5, or 1 can usually be used.

Large calculated quantities generally do not require specification of more than 3 significant digits.

For example:

ROUNDED OFFCALCULATED VALUE 3 SIGNIFICANT DIGITS

452 .61 4534526 .1 453045261 45300

More specific examples of this guide are shown in the pass out documentation.

It must be remembered that these are guides and some applications may require greater accuracy than the general recommendation.

Page 15: Dimensioning Module

MODULE # 2

Dimensioning and Tolerancing

Dimensioning Methods

Dimensioning of Features

Page 16: Dimensioning Module

Dimensioning MethodsThis standard describes recommended dimensioning methods for drawings/ models. This standard is based on American Society of Mechanical Engineers (ASME) National Standard Y14.5.

Drawings/models are to be dimensioned by one or a combination of the following practices.

•Zero plane dimensioning (dimensions are specified on extension lines without dimension lines or arrowheads).

•Dimensioning with arrowheads and dimension lines.

•Dimensioning with leaders and notes.

Page 17: Dimensioning Module

Dimensioning MethodsZero plane dimensioning is preferred on those drawings/models with many basic dimensions for features such as holes and surfaces which are to be toleranced with geometric position or profile tolerances.

ZERO PLANE DIMENSIONING

This system provides greater clarity and requires less time than the system using arrowheads and dimension lines. Zero plane dimensioning is more readily adapted to design and manufacturing processes, such as numerical controlled (NC) machining, computer aided drafting/modeling and coordinate measuring machine (CMM) inspection systems.

Definition. Zero plane dimensioning is a simplified rectangular coordinate dimensioning system in which dimensions, placed adjacent to extension lines, indicate the distance from a parallel zero plane without the need for dimension lines and arrow heads.

Page 18: Dimensioning Module

Dimensioning MethodsApplication.

Zero Plane Selection.

Number of Zero Planes.

Zero plane dimensioning may be applied to any new drawing/model or to any redrawn drawing even though dimensions with arrowheads were previously used on the drawing.

Functional surfaces or features should be selected to establish zero planes. Where practical, the functional features used to establish zero planes should be the same functional features used for geometric tolerance datums.

Only one zero plane is permitted in a given direction in each view. The same zero planes should be used in all (or as many as possible) views to maintain clear dimensional relationships between features shown in different views.

Page 19: Dimensioning Module

Dimensioning Methods

Where the zero plane dimensions in a removed view or section relate to a zero plane that is not within the view or section, repeat the zero plane adjacent to the removed view or section for reference. The reference zero plane need not be in scale to dimensions.

Zero Plane Identification.

The identification may be placed on one or both sides of each view, normally at a point beyond the dimensions measured from that zero plane. The same number is to be used in all views, which use a common plane. When a common plane is used in adjacent views, only one identification number is required between the views

Page 20: Dimensioning Module

Dimensioning MethodsDimensions.

In the principle views (front, top, right side, left side, back, and bottom), place dimensions at the end of the extension lines so that dimensions located from horizontal zero planes are read from the bottom and dimensions located from vertical zero planes are read from the right side.Either basic dimensions or dimensions with tolerances may be specified adjacent to the extension lines.

In auxiliary views and removed views, normally zero planes and extension lines are either parallel to or perpendicular to the line of projection for the view. Place dimensions at the end of extension lines and oriented parallel to the extension line.

Dimensions at extension lines inclined 45 degrees or less to horizontal are read from the bottom and dimensions at extension lines inclined less than 45 degrees to vertical are read from the right side.

Features located with basic dimensions must be toleranced with geometric profile or position tolerances.

Dimensions are normally placed outside the outline of the view.

Page 21: Dimensioning Module

Dimensioning MethodsWhere tolerances are applied directly to a zero plane dimension in which the related zero plane is a feature centerline, the position and a note must establish orientation of the zero plane as follows:

For Pro/E drawings/models:

Do not specify this note when all features are toleranced with geometric tolerances.

Drawings/models dimensioned with the zero plane system may also have features dimensioned with dimension lines and arrowheads using either basic or toleranced dimensions.

Page 22: Dimensioning Module

Dimensioning MethodsDIMENSIONING WITH ARROWHEADS AND DIMENSION LINES

Use a dimension line, with its arrowheads, to show the direction and extent of a dimension. Break dimension lines to insert numerals as shown.

REFER TO PRODUCT AND PROCESS STANDARDS B2.2.

Where a point is intended to be located by extension lines only, the extension lines from surfaces should pass through the point.

Page 23: Dimensioning Module

Dimensioning MethodsDIMENSIONING WITH LEADERS AND NOTES.

A leader (leader line) directs a dimension, note, or symbol to the intended place on the drawing/model. Normally a leader terminates in an arrowhead on the component outline. However, where a leader refers to a surface by ending within the component outline of that surface, the leader should terminate in a 1mm diameter dot; and where a leader refers to a line intersection or tangency point, the leader should end 2mm from the intersection without a terminator (no arrowhead or dot).

Page 24: Dimensioning Module

Dimensioning MethodsOTHER RULES

Dimensions with dimension lines and arrowheads shall be placed to be read from the bottom. Dimensions and notes shown with leaders are read from the bottom.

Référence Dimensions.

Indicate reference dimensions by enclosing the dimension within parentheses.

Where an overall dimension is given, one intermediate dimension is omitted or identified as a reference dimension.

Where the intermediate dimensions are more important than the overall dimension, the overall dimension, if specified, is identified as a reference dimension.

Page 25: Dimensioning Module

Dimensioning MethodsDIMENSIONS FOR PATTERNS OF HOLES

Hole patterns in mating components may be dimensioned identically to provide direct dimensional comparison when practical. When using zero plane dimensioning, dimensions may be different for corresponding hole patterns unless the same zero planes are selected on all of the mating components.

Noncircular hole patterns with repetitive dimensions for equally spaced holes may be dimensioned with dimension lines and arrowheads.

Equally Spaced Holes in Non Circular Pattern

Locating the holes in relation to datum features using a combination of coordinate and angular dimensions should dimension holes on the face of an arc. Both the angular and coordinate dimensions should be basic dimensions.

Holes on The Face of an Arc

Page 26: Dimensioning Module

Dimensioning MethodsDIMENSIONS FOR PATTERNS OF HOLES

Holes on the face of an arc and holes that are at angles other than 90 degrees to the predominant orientation of the component should be designed in angular increments of whole degrees when possible.

Numerically controlled machines are capable of working in angular increments of 1 degree (without special fixturing) which provides considerable cost savings.

Slotted or elongated holes should be dimensioned by locating the center of each slot as shown.

Refer to Standard J1.6 for recommended sizes and applications of slotted holes

Page 27: Dimensioning Module

MODULE # 2

Dimensioning and Tolerancing

Dimensioning Methods

Dimensioning of Features

Page 28: Dimensioning Module

Dimensioning of FeaturesSymbolsDiametersRadii, Arcs, & Irregular OutlinesChamfersDeburr Requirements

Threads

SquaresSlotted HolesSpot face, Counter bore, & Countersink

Milling CutterKey slots & Keyways

KnurlingMachine Centers

Conical Taper

Dimension Origin Flat Taper (Slope)

P&P standard B2.3 contains dimensioning methods to be used for the various features and characteristics of components. This standard is based on American Society of Mechanical Engineers (ASME) National Standard Y14.5.

Page 29: Dimensioning Module

Dimensioning of FeaturesDIAMETERS Place the symbol before all dimensions of diameters.The symbol and the dimension are not separated by a space.

Specify adjectives, which modify diameter before the symbol. For example; PITCH∅, or GAGE∅.

Specify adjectives, which modify the dimension after the value. For example; ∅50 MIN, ∅30.1±0.1 AVG and ∅10-B THRU.

Multiple diameters shown as concentric circles and dimensioned by a note type dimension shall have the arrowhead directed to the circle, which represents the largest visible feature dimensioned by the note.

Page 30: Dimensioning Module

Dimensioning of FeaturesRADII, ARCS, AND IRREGULAR OUTLINES

Place the symbol R, SR or CR before all dimensions of radii. The symbol and the dimensions are not separated by a space.

Specify adjectives, which modify radius before the symbol. For example; TRUE R, and ROOT R.

Specify adjectives, which modify the dimension after the value. For example; R15 MAX and R10 MIN.

Accepted methods of dimensioning radii, spherical radii, controlled radii, arc length, arcs, and irregular outlines as shown.

Arc length as shown.

This is a linear dimension measured on a curved outline.

The symbol is placed above the dimension.

Page 31: Dimensioning Module

Dimensioning of FeaturesTolerance Zone.

Tolerance zones for radii and controlled radii with and without the center located.

R MAX with profile tolerance.

Refer to Standard B3.5 for profile tolerancing.

Page 32: Dimensioning Module

Dimensioning of FeaturesRadius Tolerance.

A radius symbol R creates a zone defined by two arcs (the minimum and maximum radii). The part surface must lie within this zone.

Controlled Radius Tolerance. A controlled radius symbol CR creates a tolerance zone defined by two arcs (the minimum and maximum radii) that are tangent to the adjacent surfaces. When specifying a controlled radius, the part contour within the crescent-shaped tolerance zone must be a fair curve without reversals. Additionally, radii taken at all points on the part contour shall neither be smaller than the specified minimum limit nor larger than the maximum limit.

Application.

Radii are normally specified for inside corners to provide uniform transition between the surfaces. Specific radius application information is shown in other standards such as: SUBJECT STANDARD

Metal Working Section H7Tubes Section J9

Page 33: Dimensioning Module

Dimensioning of FeaturesRecommended Radii.

Recommended Sizes for Machined Radii Tolerances for radius dimensions may be specified individually with the dimension or as a profile tolerance with the dimension shown as basic.CAUTION: Basic radius dimensions that are smaller than the profile tolerance should not be specified because this permits the tolerance zone to become a sharp corner at minimum size for outside corners or at maximum size for inside corners.

Radius Maximum (RXX MAX).

Place R before and MAX after all dimensions of corners that may be sharp, a radius, or a similar contour that lies between a sharp corner and the radius.

Show inside corners as radii and outside corners as sharp representing the maximum material condition that must be considered on mating components.

Page 34: Dimensioning Module

Dimensioning of FeaturesCHAMFERS

Tolérance Zone. The chamfer angle, which is basic, together with the tolerances applied to one of the sides or legs establishes a tolerance zone as shown.

Dimensioning Methods. Methods of dimensioning chamfers are illustrated as follows:

Diameter and Angle Method.This method is required for chamfers on the ends of shafts, pins, bushings, etc., particularly where additional material is removed from the inside or outside diameter after the chamfer is produced.

Side and Angle Method.The length of one side and the angle may be dimensioned as shown in

Page 35: Dimensioning Module

Dimensioning of FeaturesNote Method.This method is used only for 45 chamfers.The linear value applies to either leg or side of the chamfer.

This method may be used for chamfers with side’s 25 mm or smaller.

Chamfers on Threads.Chamfers on internal and external threads shall be dimensioned as shown.

Recommended chamfer sizes and tolerances:

For Machined Chamfers

Page 36: Dimensioning Module

Dimensioning of FeaturesMaximum Chamfer. Place MAX after all chamfer dimensions of corners that may be a 45 chamfer a sharp corner, or a contour that lies between a chamfer and a sharp corner.

Show inside corners as 45 chamfers and outside corners as sharp representing the maximum material condition that must be considered on mating components.

Application. Chamfers are normally specified for outside corners to remove the sharp corner.

Specific chamfer application information is shown in other standards such as those listed below:

SUBJECT STANDARDBearings - Antifriction Section J8Bearings - Sleeve Section J8Pins - Clevis Section J1Seals - O Ring Section J11Seals - Lip Type Section J11Threads Section J1

Page 37: Dimensioning Module

Dimensioning of FeaturesDEBURR REQUIREMENTS

Application. 1E0009 Deburr Requirements specification provides deburr requirements for metallic components unless otherwise specified on the drawing/model and is applied as part of 1E0011 Interpretation and Tolerance specification.

Do not specify 1E0009 on any drawings/models. Requirements Specified in 1E0009.

a. Gray Iron Castings. Specification 1E0009 controls burrs on specific features that are listed and requires removal of all loose or hanging burrs. When further deburring is a functional requirement, it must be specified using one of the deburr notes.

Specific features covered in 1E0009 are as follows:1. Intersections of holes for oil and fuel passages. 2. Hydraulic valve body o-ring grooves, stem and spool bore lands, and other machined surfaces.

b. Other Metallic Materials. Specification 1E0009 controls burrs on all machined edges. Deburr notes may be used to override these controls when the functional requirement will.

1. Permit larger burrs to remain. 2. Permit removal of more material. 3. Require closer control of the edge.

Page 38: Dimensioning Module

Dimensioning of FeaturesControls are listed in 1E0009 for the following:

1. Loose or hanging burrs.

6. Burrs formed by cutting processes.(chip producing, abrasive, shear type, nibbling, and flame cutting processes).

2. Mechanical joint hydraulic tube fitting bore and grooves.3. Gear and spline teeth.4. Key-slots in shafts.5. Cutoff burr on ends of bar-stock.

Deburr Notes. Deburr control for specific edges may be applied by using one of the following deburr notes.

Interpretations are covered in 1E0009.

DEBURR – 1 Due to the high cost of meeting this requirement, this note should not be specified if any of the other deburr notes can be used.

DEBURR - 2, DEBURR - 3, DEBURR - 4, DEBURR - 6Use as required.

X.X MAX BURR PERMITTED.May be used when it is determined that the burr will not adversely affect functional requirements.

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Dimensioning of FeaturesSLOTTED HOLES

Accepted methods of dimensioning the width and length of slotted holes.

Two methods of using boundary position tolerance are shown.

The end radii are indicated but not dimensioned.

These methods using boundary position tolerance are utilized for slots controlled by 1E0421.

This method should be utilized for slots which are not controlled by 1E0421. (Cast or flame cut)

Page 40: Dimensioning Module

Dimensioning of FeaturesSPOTFACE, COUNTERBORE, AND COUNTERSINK

Place the symbol (⊔) before the diameter symbol and dimension.

Spot face depth is not normally specified.

Where the spot face depth is not specified 1E0011 specification requires a minimum depth that will clean up at least 90% of the surface within the specified diameter and limits the maximum depth by the minimum material condition established by the casting or forging profile tolerance zone.

Where required, the depth (or if more significant, the remaining thickness of material) is specified as shown.

Spotface

Page 41: Dimensioning Module

Dimensioning of FeaturesCounterbore.

Specify the diameter, depth, and corner condition as shown.

Place the symbol (⊔) before the diameter symbol and dimension.

Where the remaining material thickness is more significant, thickness is dimensioned rather than the depth.

Refer also to Standards Section J1.

Page 42: Dimensioning Module

Dimensioning of FeaturesCountersink.

Place the countersink symbol () before the diameter symbol and dimension.

Where the countersink is on a flat surface, specify the diameter, included angle and, where required, the depth (or if more significant, the thickness of the remaining material).

Where the countersink is on a curved surface, specify a length dimension and included angle.

The depth dimension for a countersink is the depth of the full diameter of the countersink measured from the outer surface of the component.

Page 43: Dimensioning Module

Dimensioning of FeaturesTHREADS

Methods of showing thread representations and designations,refer to Standard Section J1.1E2650 Specification indicates the thread limits and inspection practices for standard millimeter screw threads, it must be specified on components which have metric threads specified.

MILLING CUTTER Dimension the radius formed by the milling cutter by specifying the cutter diameter and location of its center.

Specify the cutter diameter as either a maximum or minimum dimension when possible.

Specify milling cutter size in 10-mm increments. Where possible use metric sizes, which encompass standard inch cutter sizes.

KEYSLOTS AND KEYWAYS

Specific keyway and keyslot selection and application information is shown in Standard Section J4.

Page 44: Dimensioning Module

Dimensioning of FeaturesKNURLING Knurling is normally used to roughen a surface to provide a better grip.

Additional information for knurling is available in ASME B94.6.Refer to Product & Process standards B2.3 for Caterpillar application methods.

MACHINE CENTER Machine centers are normally required for producing cylindrical components.

The 1E0344 callout listed in the A3 specification numerical index shall be placed in the specification block. Additional information is required on the drawing/model to indicate the size and type of centers, refer to P & P standard B2.3

1E0344A (Optional) Center 1E0344B (Required) centers.

CONICAL TAPER Conical taper is specified as a unit less ratio, which expresses change in diameter per unit of length.

Specify basic taper, gage diameter, and toleranced gage diameter locating dimension.

Page 45: Dimensioning Module

Dimensioning of FeaturesFLAT TAPER A flat taper may be specified by a toleranced slope and a toleranced height at one end.

Slope may be specified as the inclination of a surface expressed as a ratio of the difference in the heights at each end (above and at right angles to a base line) to the distance between those heights. Thus, slope = (H - h)/L

DIMENSION ORIGIN

The origin symbol is used to indicate the point from which a dimension is measured.

The preferred method is to use geometric tolerancing, which establishes a datum reference frame.

Page 46: Dimensioning Module

FunctionWhere & how does the design function, exist and/or reside?

Define Datum requirementsFeature(s) which establish component in next higher level (3D)

How is it mounted? What locates it? What orientates it?(Primary datum) (Secondary Datum) (Tertiary)

What does the design require?Define control/s required

Material,Feature sizes and tolerances,Geometric Tolerances,Location tolerances

Form & FitWhat are the dimensions?

-Design __ Ensure Functional Requirement’s-Graphics_ Models & Drawings-Text ____ Notices (Release and Change)

Surface Texture requirement, Welding requirement, Heat Treat requirement, Assembly and Disassembly requirement , Component Performance and Life, ..etc.


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