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