eas 3711 dimensioning and tolerancing

of 37 /37
Dimensioning & Tolerancing Dr. Fairuz I. Romli Semester 2 2009/2010

Author: jinhantu

Post on 20-Jan-2015

1.139 views

Category:

Documents


2 download

Embed Size (px)

DESCRIPTION

 

TRANSCRIPT

  • 1. Dimensioning & Tolerancing
    Dr. Fairuz I. Romli
    Semester 2 2009/2010

2. Introduction: Dimensioning
Working drawings must show dimensions and contain notes conveying sizes, specifications and other information
Techniques of dimensioning presented are based primarily on the standards of the American National Standards Institute (ANSI)
Two commonly used units of measurement
Metric units in millimeter round the millimeters to the nearest whole number
English units in inches
always show up to two decimal
places, even for whole numbers
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
3. Dual Dimensioning
On some drawings, both metric and English units might be required
Place the millimeter equivalent either under or over the inch units
Place the converted dimension in brackets to the right of the original dimension
Be consistent in the arrangement throughout the whole drawing
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
4. Metric Designation
In metric system (SI)
First-angle projection positions the front view over the top view and the right-side view to the left of the front view
American system use third-angle projection places top view over the front view
Label metric drawings with one of the symbols
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
5. Numeric & Symbolic Dimensioning
Vertical dimensions aligned or uni-directional
Uni-directional all dimensions appear in the standard horizontal position
Aligned numerals are parallel with vertical and angular dimension lines and read from the right-hand side of the drawing, never from the left-hand side
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
6. Numeric & Symbolic Dimensioning
Placement
Dimensions should be placed on the most descriptive views of the part being dimensioned
First row of dimensions should be at least 3 times the letter height (3H) from the object
Successive rows of dimensions should be spaced equally at least 2 times the letter height (2H)
Regardless of space limitations numerals have to be the same size throughout the entire drawing
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
7. Numeric & Symbolic Dimensioning
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
8. Numeric & Symbolic Dimensioning
Symbols
To save some drawing times use these symbols instead of words
Size usually based on the letter height often 1/8 inch
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
9. Dimensioning Rules
To place dimensions and notes on drawings most effectively
However, from time to time, rules of dimensioning must be violated due to the complexity of the part or shortage of space
Rules for prisms
Place the first row of dimensions at least 3H from the object
Successive rows at least 2H from each other
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
10. Dimensioning Rules
Rules for prisms
Place the dimensions between the views sharing these dimensions
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
11. Dimensioning Rules
Rules for prisms
Place the dimensions on the most descriptive views of an object
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
12. Dimensioning Rules
Rules for prisms
Dimension visible features, not hidden features
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
13. Dimensioning Rules
Rules for prisms
Leave the last dimension blank in a chain of dimensions when you also give an overall dimension
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
14. Dimensioning Rules
Rules for prisms
Place dimensions in well-organized lines for uncluttered drawings
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
15. Dimensioning Rules
Rules for prisms
Do not duplicate dimensions on a drawing to avoid errors or confusion
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
16. Dimensioning Rules
Rules for prisms
Dimension lines should cross any other lines unless absolutely necessary
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
17. Dimensioning Rules
Rules for prisms
Extension lines may cross other extension lines or object if necessary
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
18. Dimensioning Rules
Rules for prisms
Leave a small gap from the edges of an object to extension lines that extend from them. Do not leave gaps where extension lines cross object lines or other extension lines
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
19. Dimensioning Rules
Rules for prisms
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
20. Dimensioning Rules
Rules for angles
Place angular dimensions outside angular notches by using extension lines
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
21. Dimensioning Rules
Rules for angles
Dimension a bent surface rounded corner by locating its theoretical point of intersection with extension lines
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
22. Dimensioning Rules
Rules for cylindrical parts and Holes
Dimension the diameter (not the radius) of a cylinder in the rectangular view
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
23. Dimensioning Rules
Rules for cylindrical parts and Holes
Dimensions on concentric cylinders are easier to read if they are staggered within their dimension lines
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
24. Dimensioning Rules
Rules for cylindrical parts and Holes
Dimension holes in their circular view with leaders whenever possible, but dimension them in their rectangular views if necessary
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
25. Dimensioning Rules
Rules for cylindrical parts and Holes
Draw leaders pointing toward the centers of holes
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
26. Dimensioning Rules
Rule for leaders
Extend leaders from the first or the last word of a note with a horizontal elbow
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
27. Dimensioning Rules
Rule for arcs and radii
When space permits, place dimensions and arrows between the center and the arc
When space is not available for the numbers, place the arrow between the center and the arc number outside
If there is no space for the arrow inside, place both the dimension and arrow outside the arc with a leader
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
28. Dimensioning Rules
Rule for location dimensions
Locate cylindrical holes in their circular views by coordinates to their centers
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
29. Introduction: Tolerancing
Technique of dimensioning parts within a required range of variation
Each dimension is allowed a certain degree of variation within a specified zone
A tolerance should be as large as possible without interfering with the function of the part to minimize production costs
Manufacturing costs increase as tolerances become smaller
Positioning of tolerances
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
30. Rules of Tolerancing
Order of numbers
Place upper limits either above or to the right of lower limits
In plus minus tolerancing, place the plus limits above the minus limits
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
31. Rules of Tolerancing
Positioning of numbers
Spacing and ratios of numerals used to specify tolerances on dimensions
Earle, J. H. Graphics for Engineers, Addison-Wesley Publishing, 1996
32. Q1
33. Q1
34. Q1
35. Q2
36. Q2
37. Q2