Chapter 8/9Dimensioning/Tolerancing

Agenda

Chapter 8: DimensioningTerminology and ConventionsLinear DimensionsDimension Styles, Scale, UnitsAlignedRadius and DiameterAngularOrdinate, Continue, Quick LeaderHolesApplications to Sectional and Orthographic views

Linear Dimensioning MethodsSelect linear dimension, start, end, move, clickFor vertical same, except may need type VSelect linear dimension, R-click, select object

Change Text

Change Text in Dimension (fig 8-7)Start Dimension, after selecting 2nd extension line, type t, then 5 x 1.5 (7.50) You may also type m for Mtext and use dialogueTo edit an existing dimension, use dimension text edit tool change style or justificationTo edit dimension text, choose the A dimension symbol

Dimension StylesWeve used this to change center marks to linesAlso can change the scale of measurements for drawings not-to-scalePrimary units tabDimensions must always reflect true sizeDoes the preview reflect change in scale?Also can change text size & placementText tab, modify height, alignment, placement

Different Format Requirements for Millimeter and Inches drawings

UnitsAll dimension values are given default tolerances for manufacturing, for example:

Therefore a dimension of 5.50 means less tolerance than 5.5000Again, go to Dimension Styles>Primary UnitsExperiment with leading zero suppression (needed for inches drawings)Experiment with precision, and format

Aligned DimensionsCan be by selecting extension lines

and by selecting objectHit return after starting, select line, and locationYou may type M, T for text options, A for angle of text

Radius and Diameters

Radius and DiametersRule: arcs use radius, circles use diameterAny arc > 180 degrees use diameterRadius: select arc, position dimension leader line is neither horizontal nor verticalModify text by typing M, type 4 PlacesCan remove center pt mark: syms&arrows/noneCircles: need diameter value + center pt infoChange center pt to center lineTweak the scale factor so line crosses edge Add horizontal and vertical dimensions to circleThen add diameter dimensionangle leader line

Do NOT over-dimensionAngle Dimension

Angle Dimension Rule: arcs use radius, circles use diameterAny arc > 180 degrees use diameterRadius: select arc, position dimension leader line is neither horizontal nor verticalModify text by typing M, type 4 PlacesCan remove center pt mark: syms&arrows/noneCircles: need diameter value + center pt infoChange center pt to center lineTweak the scale factor so line crosses edge Add horizontal and vertical dimensions to circleThen add diameter dimensionangle leader line

ORDINATE DIMENSIONS

ORDINATE DIMENSIONS

Ordinate DimensionsBased on X-Y coordinate system.No extensions, arrows, etcUseful when there are lots of circles to place center points

Ordinate DimensionsFirst, relocate the originTools>New UCS>OriginClick on lower left cornerTurn on ORTHO buttonSelect Ordinate Dimension ToolSelect lower endpoint of circle centerlineSelect point on X-axis directly below centerlineRight-click to repeat on other featuresExtend centerlines as needed Add diameter dimension for holes

BASELINE DIMENSIONS

Baseline DimensionsUsed to show a series of dimensions originating from a baseline Eliminate tolerance buildup associated with chain type dimensionsOnly use after an initial dimension drawnLinear Dimension first (nearest object)Select baseline toolContinue to select extension lines for remaining objects

CONTINUE DIMENSIONS

Continue DimensionChain dimensions based on initial linear/angular/ordinate dimensionPlace first linear dimensionChoose Continue dimensionContinue placing new dimensions along edge of object

QUICK DIMENSION TOOL

Quick DimensionInserts many dimensions at onceLets you select a number of extension lines, Then c for continue OR o for ordinate

QUICK LEADER TOOL

Quick LeaderLeaderslanted lines that extend from notes or dimensions to a specific feature on the drawingUsually end with an arrowhead or dotSame as Radius and Diameter but used when no circle presentClick Leader toolstart point (arrowhead), end point (of slant)End point (of horizontal line) then textCurved line possible if type s after clicking on tool

HOW TO DIMENSION HOLES

HOLES IN SECTION VIEWS

HOLE PATTERNS

FILLETS AND ROUNDSAre usually the same sizecan use a note:

PLACEMENT OF DIMENSIONS

PLACEMENT OF DIMENSIONS

PLACEMENT OF DIMENSIONS

PLACEMENT OF DIMENSIONS

SECTIONAL VIEWS may need to adjust section angle for dimension line visibility

ORTHOGRAPHIC VIEWSDo not double-dimensionHoles dimension in circle viewGOALMinimum Dimensions needed to completely define all features

AgendaChapter 9TolerancingDirect toleranceTolerances in Inches and MillimetersPlus and minus tolerancesLimit tolerancesAngular TolerancesChain vs Baseline Dimensioning : effect on tolerance

MILLIMETER STYLE

INCHES STYLE

ACCEPTABLE OBJECTS,Millimeters+/- Tolerances

ACCEPTABLE OBJECTS,INCHES STYLE+/- Tolerances

AutoCAD Plus/Minus TolerancesText optionLinear dim, t, type text 5.00%%p.02 for +/-Mtext optionLinear dim, m, click to right of value, %%p, etc.dimension style/primary units to set precisionUsing DtextType dtext, place start, define ht/angle, type dim5.00%%p.02, then enterDimension Styles sets for all future dimsModify/tolerances/ method/symm, value(or deviation, 2 values)

LIMIT TolerancesSame meaning, easier to read

LIMIT Tolerances with dimension style toolbar

LIMIT Tolerances with dimension style toolbar

LIMIT Tolerances with dimension edit toolbar(When only a few need limit dimensions)

ANGULAR Tolerances with dimension style toolbarSame as for linear, use Mtext or text option

CAUTION!!! Double Dimensions

CHAIN vs BASELINE and tolerances