Dimensioning

Dimensioning 2º eso

1. THE REPRESENTATION OF OBJECTS DIMENSIONING

2. What is dimensioning ? When we design an object , we make a sketch or a plan. If we are going to build it , we´ll need how it is and, further , its dimensions . Representation on objects With this information , we can go to the workshop and built it , or give it to other person and order him it .

3. Representation on objects Each of the individual measures is called dimension . The process of establishing correspondences between the dimensions of our drawing and those of real- world objects is called dimensioning . What is dimensioning ?

4. Dimensioning Let´s dimension the width of this rectangle to learn how to do it . Representation on objects As it is a standardized process , you must follow some steps . Dimensioning is a standardized process we must always apply when drawing .

5. Dimensioning FIRST STEP Draw the reference lines Representation on objects They are two short lines that extend outwards perpendicularly from the section whose dimension we wish to indicate . They must be drawn with fine lines . Reference lines

6. Dimensioning SECOND STEP Draw the dimension line Representation on objects It is a line drawn between two reference lines , parallel to the dimension we wish to indicate . It must be drawn with a fine line too . It must be separated about 8 mm from the the dimension we wish to indicate . The reference lines stand above about 2 mm from the dimension line. Dimension line About 8 mm About 2 mm

7. Dimensioning THIRD STEP Draw the arrowheads Representation on objects They are two arrows drawn at the each end of the dimension line . The arrow´s tip is an angle of 20º They must be filled Arrowhead

8. Dimensioning FOURTH STEP Write the dimension value Representation on objects It´s the number that indicates the real value of the measure . You mustn´t write the value but draw it . It´s always centred on the dimension line. The dimension is always expresed in mm, so there is no need to use the mm abbreviation . It´s placed above the dimension line ( looking from down to up and from right to left ) 40 Dimension value

9. Dimensioning And now , let´s dimension the height Representation on objects 40 Remember all the steps 40 40 40 40 25 Reference lines Dimension line Arrowheads Dimension value

10. Some rules In order to properly indicate the dimensions of an object , we should take into account some recommendations : Representation on objects Indicate all dimensions . If any dimensions are missing , it will be impossible to construct the item for lack of information . 40 Could you draw a rectangle like this ? No, you need to know its height .

11. Some rules In order to properly indicate the dimensions of an object , we should take into account some recommendations : Representation on objects Avoid redundant dimensions Is necessary this dimension ? No, because it is the same that the right side . 40 25 25

12. Some rules In order to properly indicate the dimensions of an object , we should take into account some recommendations : Representation on objects Avoid those dimensions easily deducible from dimensions already indicated . Is necessary this dimension ? No, because you can calculate it by substracting 50-15 50 1 5 35

13. Some rules If it is possible , don´t use the outline of the piece as a dimension line. Representation on objects 48 48

14. Some rules If the arrowheads don´t fit in the dimension , you´ll draw them outside . Representation on objects And if there is no place for the dimension value , you´ll draw it outside too . 8 8 3

15. Some rules You must avoid dimension lines to be crossed . Representation on objects Unless it´s impossible . 10 40 10 40 42 40

16. Three ways to dimensioning a drawing CHAIN DIMENSIONING The individual dimensions are in the same line Representation on objects PARALLEL DIMENSIONING The individual dimensions are originated from the same line point COMBINED DIMENSIONING It’s a combination of chain a parallel dimensioning

17. Some rules When dimensioning circumferences , the reference lines are itself . Representation on objects 28 8 I f the dimension value does not fit in it , we will draw it and the arrowheads out . And we will dimension concentrical circunferemces in this way 28 20

18. Some rules And when dimensioning arcs measuring less than 180º), we must dimension the radius . Representation on objects I f the dimension value or the arrowhead do not fit in it , we will draw it in this way . R12 R4 The dimension value is preceded by the letter R It must be indicated the center of the circle There is no arrowhead in this edge of the dimension line

19. You must remember Dimension provide two types of information : The location of a feature The size of a feature Representation on objects Location Size

20. Reviewing Representation on objects 40 25 40 25 40 25 40 25 40 There are two redundant dimensions There is a dimension left

21. Reviewing Representation on objects 40 The dimension line is too near from the outline of the piece 40 40 The dimension line is too far from the outline of the piece 40 40 40 The arrowheads are too long The arrowheads are too thick

22. Reviewing Representation on objects 40 25 40 25 40 25 40 25 40 25 40 25 The dimension value must be placed above the dimension line ( looking from down to up and from right to left )

23. Reviewing Representation on objects 40 The reference lines stand above less than 2 mm The reference lines stand above more than 2 mm The dimension value is on ( not above ) the dimension line The dimension value is not centered 40 40 40 40 40

24. Examples Representation on objects

25. Examples Representation on objects

26. Examples Representation on objects The purpose of dimensioning is to provide a clear and complete description of an object. A complete set of dimensions will permit only one interpretation needed to construct the object, although the set of dimensions is not an only one. So, dimensioning should follow these guidelines: Accuracy: correct values must be given . Clearness: dimensions must be placed in appropriate positions . Completeness: nothing must be left out, and nothing duplicated. Readability : the appropriate line quality must be used for legibility.