3. OBJECTIVES
At the end of this lesson, students will be able to:
Define the term dimensioning
Recognize the rules for proper dimensioning
Explain the different types of dimensioning techniques
Illustrate the different dimensioning techniques
Dimension any plane and irregular figure
Value the purpose of dimensioning
4. WHAT IS A DIMENSION?
In Technical Drawing, dimensions are:
a numeric value expressed in measureable units
such as, mm, cm, inches, etc. that define the
size, location, or orientation of a geometrical
part or object.
A method of communication for persons in the
industries.
5. WHAT IS THE PURPOSE OF
DIMENSIONING?
The purpose of dimensions is to provide a clear
and complete description or measurement of an
object or part.
To communicate numeric values for a
particular geometrical part or object.
6. WHEN DO WE USE DIMENSION?
We use dimensions when details of a particular
geometrical part or object is needed.
Dimensions should be done on all drawings
that will be interpreted later on.
7. HOW DO WE DIMENSION?
In Technical Drawing, we must dimension with:
Accuracy - correct values must be given.
Clearness - dimensions must be placed in
appropriate positions.
Completeness - nothing should be left out, and
nothing duplicated.
Readability - the appropriate line quality must be
used for legibility.
18. RULES FOR DIMENSIONING
Dimensions that are not
needed should not be given.
When the overall dimension is
given, one of the smaller ones
should be eliminated.
19. RULES FOR DIMENSIONING
On a part with a circular
end, dimension to the
centerline.
Always give the diameter of
a circle, not the radius. Use
symbol Ø.
20. RULES FOR DIMENSIONING
Always give the radius of an
arc, with the abbreviation ‘R’
given before dimension text.
Do not use a centerline or a
part of an object as a
dimension line.
