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Dimensioning. Why do we use Dimensions?  Size and  Location of all features Engineers, designers, and engineering technologists need to know.

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Presentation on theme: "Dimensioning. Why do we use Dimensions?  Size and  Location of all features Engineers, designers, and engineering technologists need to know."— Presentation transcript:

1 Dimensioning

2 Why do we use Dimensions?  Size and  Location of all features Engineers, designers, and engineering technologists need to know

3 What is Dimensioning? Placing numbers (MEASUREMENTS) on a drawing Those numbers show SIZE & LOCATION SIZE shows how big or small a feature is LOCATION explains exactly where something exists in a view Remember, we draw three views: the front view, top view, and side view

4 How do we Dimension? It is important to try to include enough dimensions on a drawing to adequately describe an object (but not too many) It is also very important we locate those dimensions in the CORRECT place Most dimensions should be drawn between views (between the front and top views or between the front and side views)

5 How to Dimension We will need lines with arrows that show length or size of something on a view We will need a spot for those arrows to point (beginning and ending spots) We will need to place a measurement on our drawing within that arrow We need to put all this information in the best possible (correct) location on our drawing

6 Dimension Completely Width

7 Dimension Completely Height Width

8 What “three” Dimensions? Depth Width Height

9 Three types of LINES used… There are mainly three types of lines used when drawing dimensions EXTENSION LINES DIMENSION LINES LEADER LINES Notice the explanations on the next slides

10 Extension Lines… Extension lines are the lines that stick out from a corner or edge of a view Look at the drawing again and pay close attention to the examples of extension lines that “extend” out from a corner but DO NOT TOUCH any construction line This is where the “arrows” will point (touch)

11 Dimension Line “Types” again: Dimension Line Extension Line Leader Line

12 Dimension Lines… Now, look at the lines with the arrows on each end These lines are drawn from extension line to extension line These “dimension lines” often have a number in the middle (the distance shown) Notice the dimension lines in the next slide

13 Dimension Line “Types” again: Dimension Line Extension Line Leader Line

14 Leader Lines… Leader lines are not used as frequently, but they are still important Notice where it points Notice what it is showing Look at the slide again and pay close attention to how each line is used

15 Dimension Line “Types” again: Dimension Line Extension Line Leader Line

16 Next: Dimensioning Guidelines (Rules) Incorrect dimensions will be shown in RED Correct dimensions will be shown in GREEN

17 1) Dimensions should NOT be duplicated, nor should the same information be given in two different ways. Incorrect

18 1) Dimensions should NOT be duplicated, nor should the same information be given in two different ways. Correct

19 2) Dimensions should be attached to the view that best shows the contour (curve, shape) of the feature to be dimensioned. Incorrect

20 Take a look at this rule again… 2) Dimensions should be attached to the view that best shows the contour of the feature to be dimensioned. So, look at the drawing again (next slide). According to this rule, which view SHOULD those red dimensions be “attached to?”

21 2) Dimensions should be attached to the view that best shows the contour (curve, shape) of the feature to be dimensioned. Incorrect

22 2) Dimensions should be attached to the view that best shows the contour of the feature to be dimensioned. Correct

23 3) Don’t attach dimensions to hidden lines. Incorrect

24 3) Don’t attach dimensions to hidden lines.

25 4) Don’t dimension over or through an object. Incorrect

26 4) Don’t dimension over or through an object. (not inside any view)

27 5) Put dimensions between adjacent views. Incorrect

28 5) Put dimensions between adjacent views. Notice this dimension is not between the views; HOWEVER, this is a better placement than dimensioning to the hidden line in the right side view.

29 6) A circle is dimensioned by its diameter. An arc is dimensioned by its radius.

30 7) Holes are located by their centerlines. These lines are often drawn long enough to be used as extension lines.

31 Incorrect 8) Holes should be located and sized in the view that shows them as a circle.

32 Correct 8) Holes should be located and sized in the view that shows them as a circle.

33 Numbers 3 and 4 Read question 3 Your instructor may explain this more (Raise your hand if you have a question) Peek at the graph paper on the back of your worksheet for clarification Look at question 4 (the reverse) Take two or three minutes to answer question 3 and question 4

34 Missing Dimensions Look at the next slide and try to figure out where there are some missing dimensions Don’t forget the arrows on both ends of your dimension lines when we draw them Don’t write them on your paper yet Look at the three-view drawing and try to notice (to yourself) where a dimension is missing (#5 on the back of your sheet)

35 Can you locate where there are three Missing Dimensions? ¼ in. scale or 4 squares = 1 in.

36 Here They Are

37 Draw them…. Draw those three dimensions on your paper when that slide is repeated (next) The next slide will show the missing dimensions again Do your best to put them on your drawing as neatly and correctly as possible You will have to squeeze one of them between two other dimensions

38 Here They Are

39 Practice Dimensioning… ¼ in. scale or 4 squares = 1 in.

40 Check Your Answers

41 Directions for next two pages: Next, for each isometric sketch on the next few pages you will need to create orthographic drawings (front view, top view, and side view) …and dimension them. You will complete three examples.

42 …more… Make sure you place the front view in the lower left corner, the top view directly above the front view in the upper left corner, and the right side view to the right of the front view in the lower right corner.

43 Begin. Line up your sketches both horizontally and vertically. Add all of the dimensions necessary using the scale 1 square = ¼ in. Your dimension lines should have arrows at the end, and the extension lines you draw should not touch your object lines.

44 Homework? Work on these orthographic drawings for the remainder of class. Unless your instructor tells you differently, anything you do not finish is homework. DO NOT LOSE THIS ASSIGNMENT. Do the best you can and good luck.


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