DimensioningDimensioningStandards and Techniques

Organizations for Dimension Organizations for Dimension StandardsStandards

American National Standards Institute – a U.S. organization that recommends standards for many products in various industries. Abbreviation:  ANSI

The American Society of Mechanical Engineers (ASME) is a professional body, specifically an engineering society, focused on mechanical engineering.

The International Standards Organization - widely known as ISO, is an international-standard-setting body composed of representatives from various national standards organizations.

Functions of Functions of DimensioningDimensioning Conveys communication to the

drawingProvides clarity Describes necessary processesDescribes the scale, size, and location of features on an object

Must comply to standards

Objectives to LearnObjectives to LearnRecognition of lines

◦Dimension lines, extension lines, and center lines

◦Review alphabet of lines and relationship to dimensioning

Placement and location of dimensions◦Ease of reading, legibility, practicality,

etc.Choice of dimensions

◦Style - Fractional, decimal, metric, or dual◦Systems – aligned or unidirectional

Aligned DimensioningAligned DimensioningAligned Dimensioning – most often used in today in architectural drawings

Dimensions are

rotated on the

vertical plane

Unidirectional Unidirectional DimensioningDimensioning

Unidirectional – often used in engineering drawings

Dimensions are not rotated on the vertical plane.

Dimension LineDimension LineThin, dark, solid lineTerminated with arrowheadsIndicate direction and extent of

dimension

Dimension Line

Extension LineExtension LineThin, dark, solid lineExtends from object line to ends of dimension lineLocates position of the dimensionExtension lines do not connect to object lines

Extension Line

Dimension TextDimension TextProvides communication with regard to sizesCan also provide communication for locationProvides clarity to relationships of features

Dimension Text

ArrowheadsArrowheadsUsed to indicate extent of dimensionShould be uniform in size and styleThere are many styles and types

Arrowhead

Arrowhead Styles and Tick Arrowhead Styles and Tick MarksMarks

SolidWorks

Arrowhead

Styles

AutoCAD

Arrowhead

Styles

Dimensioning Dimensioning SymbolsSymbols

Dimension Text

Dimension Line

Extension Line

Dimension Text illustrates the actual size of an object.Dimension Line with arrow heads are drawn the length of the dimension.Extension Lines are drawn from the edges of the object that represent the dimension.

Dimension LocationDimension Location

Dimensions should be located between views whenever possible.

Dimension PlacementDimension PlacementExtension lines are located 1/16” off of the object line and extend 1/8” above the arrowhead.

Shorter dimensions are located inside of longer dimension and 3/8” away from the object line.

Longer dimensions are located outside of shorter dimensions and 1/4” away from the dimensions inside.

Dimensioning AnglesDimensioning Angles

Coordinate Method Angular Method

Coordinate Method – specifies the two location distances of the angle

Angular Method – specifies one location distance and the angle

Leader Text

Diameter Symbol

Leader Line

Leader Line drawn with arrowhead pointing to the center of the circle.Leader Symbol for diameter (O with a slash through the center).Leader Text completes the dimension for the diameter of the cylinder.

Radius Symbol

Dimensioning Circles and Dimensioning Circles and ArcsArcs

Large Arcs use center marks

Arrow can be inside of small arcs.

Small arcs do not need center marks.

Dimensioning on ContoursDimensioning on Contours

Views are drawn to describe shapes and features. Dimensions should be given where shapes are drawn.

Incorrect placement of dimensions on the drawing on the right.

Dimensioning DiametersDimensioning Diameters

Full circular objects should be dimensioned using the diameter.

Diameter annotations are represented on drills or bores.

Radii annotations for rounds and fillets.

Dimensioning Dimensioning DiametersDiameters

Remember: dimension between views whenever possible.

Dimensions are too crowded to be represented on right side view .

Diameter dimensions are better represented on left view of this drawing.

Dimensioning Radial Dimensioning Radial PatternsPatternsLocation of holes center to holes are located on a center line circle and angles based from center of figure.

Dimensioning Dimensioning CurvesCurvesLocation for curve on the gasket is based on center marks inside and outside the

figure.

Dimensioning Dimensioning CurvesCurves

Curved or noncircular shapes can be dimensioned with coordinate dimensions or datums as illustrated below:

Dimensions should be centered between extension lines except when in a stack. They are then staggered as represented above:

Leader Line Leader Line LocationsLocations

Leader lines can cross object lines and extension lines when necessary as illustrated above.

Notes with leaders are generally placed off of the drawing figure as represented here.

Dimensioning NotesDimensioning Notes

Notes should always be lettered horizontally on the sheet and be brief and clear. Wording should be standard form.

Long Break Line

Long Break Lines are used when it is best to shorten the long view of an object.

Dimension Dimension TolerancesTolerancesAllows a range of acceptable variability

Assures assemblies will fit properly

Parts can be manufactured within a range of tolerances rather than exact

High precision means high cost

Dimensioning with Dimensioning with TolerancesTolerances

The drawing illustration below represents a tolerance of 1/32 or .03125 plus or minus range of accuracy.

Dimension TolerancesDimension TolerancesTolerance stacking is avoided by dimensioning with respect to a datum base–line as illustrated on the right figure. Errors often occur in cumulative dimensions.

A – cumulative tolerances B – base-line dimensioning

Dimensioning Tips to Dimensioning Tips to KnowKnowFractional dimensions are generally

used on cabinet drawingsDecimal dimensions are used on

engineering drawingsFeet and inch dimensions are used

on architectural drawingsTolerances are dimensioned when

assembly parts are necessary

Test your knowledge on the rest of the Test your knowledge on the rest of the slides after reviewing the dimension slides after reviewing the dimension rules from your class text.rules from your class text.

What is wrong with the What is wrong with the placement location of these placement location of these dimensions?dimensions?

The longer dimensions have been positioned inside of the shorter dimensions.

What is wrong with the What is wrong with the placement location of these placement location of these dimensions?dimensions?

Dimensions should be located outside the object lines whenever possible to avoid confusion.

What is wrong with the What is wrong with the dimensions below?dimensions below?

The drawing is over dimensioned. It is not necessary to include the inside shorter dimensions.

What is wrong with the What is wrong with the dimensions below?dimensions below?

The drawing is over dimensioned. Do not repeat dimensions. They are represented only once.

What is wrong with the What is wrong with the dimensions below?dimensions below?

The dimensions are difficult to read on the right view. They should be placed on the left view.

What is wrong with the What is wrong with the dimensions below?dimensions below?

The dimension’s text should not be on the object line. Makes the dimension difficult to read.

What is wrong with the What is wrong with the dimensions below?dimensions below?The circular dimension should be dimensioned as a diameter not a radius.

The radial dimension should be dimensioned as a radius not a diameter.

What is wrong with the What is wrong with the dimensions below?dimensions below?

The vertical dimension is needed to locate the beginning of the slant.

What is wrong with the What is wrong with the dimensions below?dimensions below?

The angular dimension is difficult to read. It should be positioned off the object line.

What is wrong with the What is wrong with the dimensions below?dimensions below? Avoid

dimensioning hidden lines and poor referencing of vertical dimensions.

What is wrong with the What is wrong with the dimensions below?dimensions below?

Dimension between views whenever possible.

A better dimensioning practice.

What is wrong with the What is wrong with the dimensions below?dimensions below? The dimension

locations are fine on this drawing. What can be done to improve it?

This is an engineering drawing. Decimals units would be better.

What is wrong with the What is wrong with the dimensions below?dimensions below?

You cannot locate the proper locations for the proper position of the holes on the radial dimension without the angular distance.

Angular Dimensions

What is wrong with the What is wrong with the dimensions below?dimensions below?

The right side view and the isometric view are not necessary to complete this drawing.

The overall length of 4.75 is also not necessary to complete this drawing.

What is wrong with the What is wrong with the dimensions below?dimensions below?

Dimensions should be placed on the contour view for clarity.