1. DIMENSIONING
Sizing of drawings in Drafting has standards and guidelines.

2. Line Thickness Line Styles
Lines on an engineering drawing signify more than just the geometry of the object and it is
important that the appropriate line type is used.
Line Thickness
For most engineering drawings you will require two thickness', a thick and thin line.
The general recommendation are that thick lines are twice as thick as thin lines.
                                             
A thick continuous line is used for visible edges and outlines.
A thin line is used for hatching, leader lines, short centre lines, dimensions and projections.
Line Styles
Other line styles used to clarify important features on drawings are:
                                            
Thin chain lines are a common feature on engineering drawings used to
indicate centre lines. Centre lines are used to identify the centre of a circle,
cylindrical features, or a line of symmetry.
                                             
Dashed lines are used to show important hidden detail for example wall
thickness and holes..

3. Precedence of Lines
Visible lines takes precedence over all other lines
Hidden lines and cutting plane lines take precedence over center lines
Center lines have lowest precedence
0.6 mm
From: Bertoline, Figure 2.40/ Pg 43
Note the thickness specified for given three types of lines
The precedence of lines governs which lines are drawn when more than one line occupies the same position on a drawing.
For example the figure above shows that while a visible line takes precedence over all other lines, hidden line and cutting plane line take precedence over center lines.
Standard engineering drawing practices requires the use of standard linetypes, which are called the alphabet of lines. The sizes show the recommended line thicknesses.
0.3 mm
0.6 mm

4. For Example: 1. Visible 2. Hidden 3. Center
From Bertoline: Figure 2.38 / Pg 42
In engineering and technical drawing, it is important that hidden features be represented, so that the reader of the drawing can clearly understand the object.
Thus we need hidden lines to emphasize that those features exist and are hidden in that particular view.
We also need center lines to understand how the features defined in the 2D views translate into 3D.
NOTE: It must be emphasized that hidden lines and center lines are used only on Orthographic projection drawings, never on isometric drawings
Q: Do we need a convention for what line to show if two lines fall on top of each other?
A: Yes! Otherwise features which are more important (eg: visible lines) would be overridden by less important features (eg: hidden lines) and the resulting drawing would be interpreted inaccurately. The next slide shows the convention followed.
2. Hidden
3. Center

5. Dimensioning
A dimensioned drawing should provide all the information necessary for a finished product or part to be manufactured. An example dimension is shown below.
                                                                                                                                                                                                       
Dimensions are always drawn using continuous thin lines. Two projection lines indicate where the dimension starts and finishes. Projection lines do not touch the object and are drawn perpendicular to the element you are dimensioning.
All dimensions less than 1 should have a leading zero. i.e. .35 should be written as 0.35

6. Types of Dimensioning Parallel Dimensioning
Parallel dimensioning consists of several dimensions originating from one projection line.

7. Superimposed Running Dimensions
Superimposed running dimensioning simplifies parallel dimensions in order to reduce the space used on a drawing. The common origin for the dimension lines is indicated by a small circle at the intersection of the first dimension and the projection line.

8. Chain Dimensioning Combined Dimensions
A combined dimension uses both chain and parallel dimensioning.

9. Dimensioning of circles
(a) shows two common methods of dimensioning a circle. One method dimensions the circle between two lines projected from two diametrically opposite points. The second method dimensions the circle internally.
(b) is used when the circle is too small for the dimension to be easily read if it was placed inside the circle.

10. Dimensioning Radii
All radial dimensions are proceeded by the capital R.
shows a radius dimensioned with the centre of the radius located on the drawing.
(b) shows how to dimension radii which do not need their centres locating.

11. Tolerancing
It is not possible in practice to manufacture products to the exact figures displayed on an engineering drawing. The accuracy depends largely on the manufacturing process. A tolerance value shows the manufacturing department the maximum permissible variation from the dimension.
Each dimension on a drawing must include a tolerance value. This can appear either as:
a general tolerance value applicable to several dimensions. i.e. a note specifying that the General Tolerance +/- 0.5 mm.
or a tolerance specific to that dimension

12. Dimension Guidelines Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
Dimension Guidelines
Note: There are dozens of rules, do’s and don’ts, and guidelines associated with dimensioning. This purpose of this presentation is to introduce those guidelines that are most critical, and that students tend to have the most trouble with when first learning how to dimension drawings. Each slide has notes that provide references to textbooks that give further details on each guideline.
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Copyright 2007

13. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
1. Dimensions should NOT be duplicated, or the same information given in two different ways.
Incorrect
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Copyright 2007

14. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
1. Dimensions should NOT be duplicated, or the same information given in two different ways.
References:
Pg 337 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 109 Fundamentals of Modern Drafting by Paul Wallach
Pg 425 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 701 Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
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Copyright 2007

15. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
2. No unnecessary dimensions should be used – only those needed to produce or inspect the part.
References:
Pg 109 Fundamentals of Modern Drafting by Paul Wallach
Pg 392 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Note: In a chain of dimensions, as seen with the width and height dimensions in the front view, one of the dimensions is unnecessary and must be removed. Overall dimensions for width, height, and depth must be present.
Incorrect
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Copyright 2007

16. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
2. No unnecessary dimensions should be used – only those needed to produce or inspect the part.
References:
Pg 109 Fundamentals of Modern Drafting by Paul Wallach
Pg 392 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Note: In a chain of dimensions, as seen with the width and height dimensions in the front view, one of the dimensions is unnecessary and must be removed. Overall dimensions for width, height, and depth must be present.
Project Lead The Way, Inc.
Copyright 2007

17. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
3. Dimensions should be attached to the view that best shows the contour of the feature to be dimensioned.
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 405 & 425 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 698, 700, Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
It should be noted that the 2.00 inch dimension would be appropriately located if placed on the top view, but the front view is preferred because it is supposed to provide the most information about an object’s geometry.
Incorrect
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Copyright 2007

18. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
3. Dimensions should be attached to the view that best shows the contour of the feature to be dimensioned.
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 405 & 425 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 698, 700, Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
It should be noted that the 2.00 inch dimension would be appropriately located if placed on the top view, but the front view is preferred because it is supposed to provide the most information about an object’s geometry.
Project Lead The Way, Inc.
Copyright 2007

19. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
4. Whenever possible, avoid dimensioning to hidden lines and features.
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 134 Fundamentals of Modern Drafting by Paul Wallach
Pg 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 703 Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Incorrect
Project Lead The Way, Inc.
Copyright 2007

20. 4. Whenever possible, avoid dimensioning to hidden lines and features.
Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
4. Whenever possible, avoid dimensioning to hidden lines and features.
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 134 Fundamentals of Modern Drafting by Paul Wallach
Pg 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 703 Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Project Lead The Way, Inc.
Copyright 2007

21. Incorrect 5. Avoid dimensioning over or through the object.
Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
5. Avoid dimensioning over or through the object.
Incorrect
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 394, 404, 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 692 Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Project Lead The Way, Inc.
Copyright 2007

22. 5. Avoid dimensioning over or through the object.
Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
5. Avoid dimensioning over or through the object.
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 394, 404, 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 692 Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Project Lead The Way, Inc.
Copyright 2007

23. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
6. A dimension should be attached to only one view; for example, extension lines should not connect two views.
Reference:
Pg 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Incorrect
Project Lead The Way, Inc.
Copyright 2007

24. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
6. A dimension should be attached to only one view; for example, extension lines should not connect two views.
Reference:
Pg 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Project Lead The Way, Inc.
Copyright 2007

25. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
7. Whenever possible, locate dimensions between adjacent views.
Incorrect
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 108 Fundamentals of Modern Drafting by Paul Wallach
Pg 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Project Lead The Way, Inc.
Copyright 2007

26. 7. Whenever possible, locate dimensions between adjacent views.
Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
7. Whenever possible, locate dimensions between adjacent views.
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 108 Fundamentals of Modern Drafting by Paul Wallach
Pg 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Project Lead The Way, Inc.
Copyright 2007

27. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
8. Avoid crossing extension lines, but do not break them when they do cross.
Multiple extension line crossings may be confused for the outside corner of the part.
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 394, 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 690 Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Note: Crossing extension lines is acceptable, but excessive numbers of crossings may confuse the viewer.
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Copyright 2007

28. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
9. Whenever possible, avoid sending extension lines through object views.
Incorrect
Reference:
Pg Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Project Lead The Way, Inc.
Copyright 2007

29. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
9. Whenever possible, avoid sending extension lines through object views.
Reference:
Pg Engineering Drawing and Design 3rd Edition by David Madsen et. al.
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Copyright 2007

30. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
10. In general, a circle is dimensioned by its diameter and an arc by its radius.
References:
Pg , Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 131, Fundamentals of Modern Drafting by Paul Wallach
Pg , , 427 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg , Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Project Lead The Way, Inc.
Copyright 2007

31. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
11. Holes are located by their centerlines, which may be extended and used as extension lines.
References:
Pg 44, 340 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg , 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Project Lead The Way, Inc.
Copyright 2007

32. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
12. Holes should be located and sized in the view that shows the feature as a circle.
Incorrect
References:
Pg 351 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 109 Fundamentals of Modern Drafting by Paul Wallach
Pg 411, 427 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 693 Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Project Lead The Way, Inc.
Copyright 2007

33. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
12. Holes should be located and sized in the view that shows the feature as a circle.
References:
Pg 351 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 109 Fundamentals of Modern Drafting by Paul Wallach
Pg 411, 427 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg 693 Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Note: The top view was removed, because it is not needed to completely communicate the object’s geometry.
Project Lead The Way, Inc.
Copyright 2007

34. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
13. Do not cross a dimension line with an extension line, and avoid crossing dimensions with leader lines.
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 394, 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Project Lead The Way, Inc.
Copyright 2007

35. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
13. Do not cross a dimension line with an extension line, and avoid crossing dimensions with leader lines.
References:
Pg 342 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 394, 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Project Lead The Way, Inc.
Copyright 2007

36. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
14. Leader lines point toward the center of the feature, and should not occur horizontally or vertically.
References:
Pg 45, 344 Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg , , 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg , 703 Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Note: Slopes greater than 75° and less than 15° from horizontal should be avoided. A leader has a .25 in shoulder at one end that begins at the center of the vertical height of the lettering and an arrowhead at the other end point.
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37. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
15. Dimension numbers should be centered between arrowheads, except when using stacked dimensions, and then the numbers should be staggered.
Incorrect
References:
Pg Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 137 Fundamentals of Modern Drafting by Paul Wallach
Pg 400, 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Note: The 0.50 dimension cannot fit in between its extension lines, and is placed to the outside of the common extension line to avoid confusion.
Project Lead The Way, Inc.
Copyright 2007

38. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
15. Dimension numbers should be centered between arrowheads, except when using stacked dimensions, and then the numbers should be staggered.
References:
Pg Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 137 Fundamentals of Modern Drafting by Paul Wallach
Pg 400, 426 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Project Lead The Way, Inc.
Copyright 2007

39. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
16. Concentric circles are dimensioned in the longitudinal view, whenever practical.
Incorrect
References:
Pg Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 407 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Note: This rule applies to shafts, not to holes.
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Copyright 2007

40. Dimension Guidelines
Introduction to Engineering Design
Unit 2 – Lesson 2.2 – Dimensions and Tolerances
16. Concentric circles are dimensioned in the longitudinal view, whenever practical.
References:
Pg Engineering Drawing and Design 3rd Edition by David Madsen et. al.
Pg 407 Technical Drawing 9th Edition by Frederick Giesecke et. al.
Pg Technical Graphics Communication 3rd Edition by Gary Bertoline & Eric Wiebe
Note: This rule applies to shafts, not to holes.
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Copyright 2007

41. Drawing layout All engineering drawings should feature a title block.
The title block should include:
Title:- title of the drawing
Name:- name of the person who produced the drawing
Checked:- before manufacture, drawings are usually checked
Version:- many drawings are amended, each revision must be noted
Date:- the date the drawing was produced or last amended
Notes:- any note relevant to the drawing
Scale:- the scale of the drawing
Company name:- name of the company
Projection:- the projection system used to create the drawing