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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 1

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

1. Dimensions should NOT be duplicated, or

the same information given in two differentways.

Incorrect

1. Dimensions should NOT be duplicated, or

the same information given in two different

ways.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 2

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

2. No unnecessary dimensions should be

used –

 only those needed to produce orinspect the part.

Incorrect

2. No unnecessary dimensions should be

used  – only those needed to produce or

inspect the part.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 3

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

3. Dimensions should be attached to the view

that best shows thecontour    

 of the featureto be dimensioned.

Incorrect

3. Dimensions should be attached to the view

that best shows the contour     of the feature

to be dimensioned.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 4

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

4. Whenever possible, avoid dimensioning to

hidden lines and features.

Incorrect

4. Whenever possible, avoid dimensioning to

hidden lines and features.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 5

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

5. Avoid dimensioning over or through the

object.

Incorrect

5. Avoid dimensioning over or through the

object.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 6

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

6. A dimension should be attached to only

one view; for example, extension linesshould not connect two views.

Incorrect

6. A dimension should be attached to only

one view; for example, extension lines

should not connect two views.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 8

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

8. Whenever possible, avoid sending extension

lines through object views.

Incorrect

8. Whenever possible, avoid sending extension

lines through object views.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 9

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

9. In general, a circle is dimensioned by its

diameter and an arc by its radius.

10. Holes are located by their centerlines,

which may be extended and used as

extension lines.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 10

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

11. Holes should be located and sized in the

view that shows the feature as a circle.

Incorrect

11. Holes should be located and sized in the

view that shows the feature as a circle.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 11

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

12. Do not cross a dimension line with an

extension line, and avoid crossingdimensions with leader lines.

12. Do not cross a dimension line with an

extension line, and avoid crossing

dimensions with leader lines.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 12

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

13. Dimension numbers should be centered

between arrowheads, except when usingstacked dimensions, and then the numbers

should be staggered.

Incorrect

13. Dimension numbers should be centered

between arrowheads, except when using

stacked dimensions, and then the numbers

should be staggered.

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Dimension Guidelines

Project Lead The Way, Inc. 

Copyright 2007 13

Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

14. Concentric circles are dimensioned in the

longitudinal view, whenever practical.

Incorrect

14. Concentric circles are dimensioned in the

longitudinal view, whenever practical.

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Dimension Guidelines Introduction to Engineering Design TM 

Unit 2  – Lesson 2.2  – Dimensions and Tolerances

Multiple

extension

line

crossings

may be

confused for

the outside

corner of the

part.

15. Avoid crossing extension lines, but do not

break them when they do cross.

16. Leader lines point toward the center of the

feature, and should not occur horizontally

or vertically.