Chapter 8/9Dimensioning/Tolerancing

Agenda

• Chapter 8: Dimensioning– Terminology and Conventions– Linear Dimensions– Dimension Styles, Scale, Units– Aligned– Radius and Diameter– Angular– Ordinate, Continue, Quick Leader– Holes– Applications to Sectional and Orthographic views

Linear Dimensioning Methods

1. Select linear dimension, start, end, move, click

2. For vertical same, except may need type V3. Select 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) <enter>

• You may also type m for Mtext and use dialogue

• To edit an existing dimension, use dimension text edit tool – change style or justification

• To edit dimension text, choose the A dimension symbol

Dimension Styles

• We’ve used this to change center marks to lines

• Also can change the scale of measurements for drawings not-to-scale– Primary units tab– Dimensions must always reflect true size– Does the preview reflect change in scale?

• Also can change text size & placement– Text tab, modify height, alignment, placement

Different Format Requirements for Millimeter and Inches drawings

Units

• All dimension values are given default tolerances formanufacturing, for example:

• Therefore a dimension of 5.50 means less tolerance than 5.5000– Again, go to Dimension Styles>Primary Units– Experiment with leading zero suppression

(needed for inches drawings)– Experiment with precision, and format

Aligned Dimensions• Can be by selecting extension lines

• and by selecting object– Hit return after starting, select line, and location– You may type M, T for text options, A for angle of text

Radius and Diameters

Radius and Diameters• Rule: arcs use radius, circles use diameter

– Any arc > 180 degrees use diameter

• Radius: select arc, position dimension – leader line is neither horizontal nor vertical– Modify text by typing M, type “– 4 Places”– Can remove center pt mark: syms&arrows/none

• Circles: need diameter value + center pt info– Change center pt to center line– Tweak the scale factor so line crosses edge – Add horizontal and vertical dimensions to circle– Then add diameter dimension…angle leader line

Do NOT over-dimension

Angle Dimension

Angle Dimension • Rule: arcs use radius, circles use diameter

– Any arc > 180 degrees use diameter

• Radius: select arc, position dimension – leader line is neither horizontal nor vertical– Modify text by typing M, type “– 4 Places”– Can remove center pt mark: syms&arrows/none

• Circles: need diameter value + center pt info– Change center pt to center line– Tweak the scale factor so line crosses edge – Add horizontal and vertical dimensions to circle– Then add diameter dimension…angle leader line

ORDINATE DIMENSIONS

ORDINATE DIMENSIONS

Ordinate Dimensions

• Based on X-Y coordinate system.• No extensions, arrows, etc• Useful when there are lots of circles

– to place center points

Ordinate Dimensions

• First, relocate the origin– Tools>New UCS>Origin

• Click on lower left corner

• Turn on ORTHO button• Select Ordinate Dimension Tool

– Select lower endpoint of circle centerline– Select point on X-axis directly below centerline– Right-click to repeat on other features– Extend centerlines as needed – Add diameter dimension for holes

BASELINE DIMENSIONS

Baseline Dimensions

• Used to show a series of dimensions originating from a baseline – Eliminate tolerance buildup associated with chain

type dimensions– Only use after an initial dimension drawn

• Linear Dimension first (nearest object)• Select baseline tool

– Continue to select extension lines for remaining objects

CONTINUE DIMENSIONS

Continue Dimension

• Chain dimensions based on initial linear/angular/ordinate dimension

• Place first linear dimension• Choose Continue dimension• Continue placing new dimensions along edge

of object

QUICK DIMENSION TOOL

Quick Dimension

• Inserts many dimensions at once• Lets you select a number of extension lines,

– Then c for continue OR o for ordinate

QUICK LEADER TOOL

Quick Leader

• Leader—slanted lines that extend from notes or dimensions to a specific feature on the drawing

• Usually end with an arrowhead or dot• Same as Radius and Diameter but used when no

circle present• Click Leader tool

– start point (arrowhead), end point (of slant)– End point (of horizontal line) <enter-2x> then text– Curved 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 size…can use a note:

PLACEMENT OF DIMENSIONS

PLACEMENT OF DIMENSIONS

PLACEMENT OF DIMENSIONS

PLACEMENT OF DIMENSIONS

SECTIONAL VIEWSmay need to adjust section angle

for dimension line visibility

ORTHOGRAPHIC VIEWSDo not double-dimension

30

This would doubly define the 30 !!

Holes dimension in circle view

GOAL—Minimum Dimensions needed to completely define all features

Agenda

• Chapter 9—Tolerancing– Direct tolerance– Tolerances in Inches and Millimeters– Plus and minus tolerances– Limit tolerances– Angular Tolerances– Chain vs Baseline Dimensioning : effect on tolerance

MILLIMETER STYLE

INCHES STYLE

ACCEPTABLE OBJECTS,Millimeters

+/- Tolerances

ACCEPTABLE OBJECTS,INCHES STYLE

+/- Tolerances

AutoCAD Plus/Minus Tolerances1. Text option

– Linear dim, t, type text “5.00%%p.02” for +/-

2. Mtext option– Linear dim, m, click to right of value, %%p, etc.– dimension style/primary units to set precision

3. Using Dtext– Type dtext, place start, define ht/angle, type dim

• 5.00%%p.02, then enter

4. Dimension Styles – sets for all future dim’s– Modify/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 toolbar

Same as for linear, use Mtext or text option

CAUTION!!! Double Dimensions

CHAIN vs BASELINE and tolerances