Lesson 8
DIMENSIONING
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W E L C O M E !
W E L C O M E !
LESSON 8 OUTLINE
LESSON 8 OUTLINE
PLACING OF DIMENSION
PLACING OF DIMENSION
RULES FOR DIMENSIONING
RULES FOR DIMENSIONING
DIMENSIONING GUIDLINES
DIMENSIONING GUIDLINES
OBJECTIVES
At the end of the lesson the students should be able to;
identify and appropriately us the different methods of dimensioning;
show interpretation of the different dimensioning methods;
utilize the different dimensioning methods.
DIMENSIONING
DIMENSIONING
NOTE: CLICK on the TEXT to view more CONTENT.
The numerical value used to describe the size and geometric characteristic of a feature. Dimensions are indicated in drawing by dimension lines and numerical figures. In other words, indicating on a drawing, the sizes of the object and the other details essential for its construction and function using lines, numerals, symbols, notes, etc., is called dimensioning.
The numerical value used to describe the size and geometric characteristic of a feature. Dimensions are indicated in drawing by dimension lines and numerical figures. In other words, indicating on a drawing, the sizes of the object and the other details essential for its construction and function using lines, numerals, symbols, notes, etc., is called dimensioning.
To construct an object its shape and size must be known. Therefore, an engineering drawing, illustrating the shape, size and relevant details most essential for the construction of the object. The dimensions are given to indicate the sizes of the various features of the object and their location. It is mainly used to know the object size, the name of parts and diameter of the hole etc.
To construct an object its shape and size must be known. Therefore, an engineering drawing, illustrating the shape, size and relevant details most essential for the construction of the object. The dimensions are given to indicate the sizes of the various features of the object and their location. It is mainly used to know the object size, the name of parts and diameter of the hole etc.
There are two kinds of dimensions, size dimension and location dimension. Size dimension give the detail and overall size of the objects, while location dimensions merely locate part or parts of the object.
There are two kinds of dimensions, size dimension and location dimension. Size dimension give the detail and overall size of the objects, while location dimensions merely locate part or parts of the object.
Overall dimensions are the total thickness or height, width and length of an object, while Detail dimensions are the thickness, length and width of each part of the same object.
Overall dimensions are the total thickness or height, width and length of an object, while Detail dimensions are the thickness, length and width of each part of the same object.
TWO SYSTEM OF DIMENSIONING
TWO SYSTEM OF DIMENSIONING
METRIC vs ENGLISH SYSTEM OF MEASUREMENTS
The metric system is an internationally agreed decimal system of measurement created in France in The International System of Units (SI), the official system of measurement in almost every country in the world, is based upon the metric system. In the metric system, each basic type of measurement (length, weight, capacity) has one basic unit of measure (meter, gram, liter). Conversions are quickly made by multiplying or dividing by factors of 10. It is as simple as moving the decimal point to the right (for smaller prefixes) or to the left (for larger prefixes).
While the metric system was lawfully accepted for use in the United States in 1866, the US has not adopted the metric system as its "official" system of measurement. The US English System of measurement grew out of the manner in which people secured measurements using body parts and familiar objects. For example, shorter ground distances were measured with the human foot and longer distances were measured by paces, with one mile being 1,000 paces. Capacities were measured with household items such as cups, pails (formerly called gallons) and baskets.
TYPES OF DIMENSIONING
TYPES OF DIMENSIONING
RULES OF DIMENSIONING
RULES OF DIMENSIONING
1. Do not place dimensions on objects. Dimensions should generally be placed between views.
1. Do not place dimensions on objects. Dimensions should generally be placed between views.
2. Avoid repetition of dimensions.
2. Avoid repetition of dimensions.
3. Dimension lines should be parallel to the edge or line being measure.
3. Dimension lines should be parallel to the edge or line being measure.
4. The flares of the arrowhead should be properly made.
4. The flares of the arrowhead should be properly made.
5. The fine line in a dimension line must be strictly observed.
5. The fine line in a dimension line must be strictly observed.
It should be one-fourth the thickness of the visible line and thickness should be the same as the projection line.
It should be one-fourth the thickness of the visible line and thickness should be the same as the projection line.
Note: The dimension line is a fine line.
6. The figure or number in a dimension line should be legible and properly located.
6. The figure or number in a dimension line should be legible and properly located.
7. Dimensional figures are preferably directional.
7. Dimensional figures are preferably directional.
Undirectional dimensions may be used if the company desires them. Never mix directional and undirectional dimensions in a drawing.
Undirectional dimensions may be used if the company desires them. Never mix directional and undirectional dimensions in a drawing.
8. Use an outside dimension if the space is limited, and use an inside dimension if the space is ample wide.
8. Use an outside dimension if the space is limited, and use an inside dimension if the space is ample wide.
9. Only metric measurements should appear in drawings.
9. Only metric measurements should appear in drawings.
Use one system of measurements in every drawing.
10. Continuous dimension should be used whenever possible.
10. Continuous dimension should be used whenever possible.
Recall: All dimensions are aligned in such a way that an arrowhead of one dimension touches tip-to-tip the arrowhead of the adjacent dimension.
11. Staggered dimensioning should be used when the spaces for the dimension is narrow.
11. Staggered dimensioning should be used when the spaces for the dimension is narrow.
12. A dimension line may be terminated by a projection, visible, hidden or center line.
12. A dimension line may be terminated by a projection, visible, hidden or center line.
13. Dimension line should not be extended beyond the edge or line being measured.
13. Dimension line should not be extended beyond the edge or line being measured.
It should always touch the projection line or edge being measured.
It should always touch the projection line or edge being measured.
14. Arrowheads should point to the terminating line and not to the dimension figure.
14. Arrowheads should point to the terminating line and not to the dimension figure.
15. Let no workman add or subtract dimensions, complete all dimension needed.
15. Let no workman add or subtract dimensions, complete all dimension needed.
16. When giving the location dimensions for round holes, measure the center-to-center distance between holes and from the center line of the holes to the two nearest visible line.
16. When giving the location dimensions for round holes, measure the center-to-center distance between holes and from the center line of the holes to the two nearest visible line.
17. Place the dimension closest to the part being measured. Dimensions may be placed inside a view.
17. Place the dimension closest to the part being measured. Dimensions may be placed inside a view.
18. Never crowd dimensions.
18. Never crowd dimensions.
The dimension closest to a view should be about 7mm. Avoid aligning dimensional figures vertically.
19. Projection or extension lines should extend about 3mm from the dimension line and not closer than 1 1/2mm from the object or visible line.
19. Projection or extension lines should extend about 3mm from the dimension line and not closer than 1 1/2mm from the object or visible line.
20. Give the diameter of a circle or round hole.
20. Give the diameter of a circle or round hole.
Note: The various ways of positioning the dimension lines as shown below.
Note: The various ways of positioning the dimension lines as shown below.
21. Give the radii or arcs.
21. Give the radii or arcs.
Note: Techniques of different dimensioning arcs oof various sizes.
22. Measure angles in degree. The figures should be undirectional.
22. Measure angles in degree. The figures should be undirectional.
Note: Techniques of dimensioning angle of various sizes.
23. Dimension irregular curves by the square or base line method.
23. Dimension irregular curves by the square or base line method.
Note: points a and b are each located by two dimensions.
24. Write or print the dimensional figure properly.
24. Write or print the dimensional figure properly.
25. Use radial dimensioning for large arcs.
25. Use radial dimensioning for large arcs.
Especially those with centers out-side the drawing paper.
26. For turned pieces, put one set of dimensions on one side and the other set on the other side of the view.
26. For turned pieces, put one set of dimensions on one side and the other set on the other side of the view.
27. Metric measurements may be given in whole numbers.
27. Metric measurements may be given in whole numbers.
In this case, a note should be added to the drawing to identify the kind of dimension used. Such a note may be written as; "All dimensions are in centimeters", "All dimensions are in millimeters" or "All dimensions are in meters unless otherwise specified."
28. Dimensions may be given as noted in the drawing.
28. Dimensions may be given as noted in the drawing.
29. Avoid crossing dimensions.
29. Avoid crossing dimensions.
DIMENSIONING ISOMETRIC AND OBLIQUE DRAWINGS
DIMENSIONING ISOMETRIC AND OBLIQUE DRAWINGS
The rules to be observed in dimensioning orthographic drawings also apply to dimensioning of isometric and oblique drawings, except that when dimensioning inclined visible edges or lines, the projection lines are perpendicular to the dimension lines.
SHORT DEMONSTARATION ON DIMENSIONING: HOW TO DIMENSION
SHORT DEMONSTARATION ON DIMENSIONING: HOW TO DIMENSION
Video_f0d9aba9-982b-42f6-8578-c7a778e2b8c6.mp4LEARNING ACTIVITY
LEARNING ACTIVITY
DIRECTIONS: PRINT the ACTIVITY SHEET provided below. STRICTLY NO REVISON TO BE MADE.
A good rule of thumb is to ask yourself the question: “Could I build the object with the dimensions currently on the drawing?” If not, review the drawing and add the missing dimensions.
LESSON 8 - ACTIVITY 8.docxREFERENCES:
REFERENCES:
CONTENT SOURCE:
CONTENT SOURCE:
Manaois, German M. Drafting Volume 2: Phoenix Publishing House, Inc., 1983, Reprinted 2004
Manaois, German M. Drafting Volume 2: Phoenix Publishing House, Inc., 1983, Reprinted 2004
Krulikowski, A. (2012). Fundamentals of Geometric Dimensioning and Tolerancing (3rd ed.). Cengage Learning.
Krulikowski, A. (2012). Fundamentals of Geometric Dimensioning and Tolerancing (3rd ed.). Cengage Learning.
Spencer, H. C., Dygdon, J. T., & Novak, J. E. (1995). Basic Technical Drawing (6th ed.). Glencoe/McGraw-Hill School Pub.
Spencer, H. C., Dygdon, J. T., & Novak, J. E. (1995). Basic Technical Drawing (6th ed.). Glencoe/McGraw-Hill School Pub.
Brown, Walter C. Drafting : Published 1986
Brown, Walter C. Drafting : Published 1986
URL: https://www.theengineerspost.com/dimensioning-systems/
URL: https://www.theengineerspost.com/dimensioning-systems/
URL: https://slideplayer.com/slide/13537998/
URL: https://slideplayer.com/slide/13537998/
URL: https://qnaengine.com/what-is-dimensioning-in-engineering-drawing/
URL: https://qnaengine.com/what-is-dimensioning-in-engineering-drawing/
URL: https://openoregon.pressbooks.pub/blueprint/chapter/unit-5-dimensioning/
URL: https://openoregon.pressbooks.pub/blueprint/chapter/unit-5-dimensioning/
URL: http://engineeringessentials.com/ege5/files/ege/dim/dim_page6_ex3.htm
URL: http://engineeringessentials.com/ege5/files/ege/dim/dim_page6_ex3.htm
VIDEO:
https://youtu.be/HNlsbYi_Uvc
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