Chapter 8/9
Dimensioning/Tolerancing
Agenda
• Chapter 8: Dimensioning
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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 V
3. 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 for
manufacturing, 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
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• 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
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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
Angle Dimension
Do NOT
over-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
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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 ROUNDS
Are usually the same size…can 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 VIEWS
Do not double-dimension
Holes
dimension in
circle view
This would doubly
define the 30 !!
30
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
+/- Tolerances
ACCEPTABLE OBJECTS,
Millimeters
+/- Tolerances
ACCEPTABLE OBJECTS,
INCHES STYLE
AutoCAD Plus/Minus Tolerances
1. 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
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5.00%%p.02, then enter
4. Dimension Styles – sets for all future dim’s
– Modify/tolerances/ method/symm, value
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(or deviation, 2 values)
LIMIT Tolerances
Same 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