Lesson Plan

Instructor:
Course:
Elias Perez
Technical Drafting
Chapter 10: Dimensioning
Unit: 10
Date:
Explain why dimensions and notes are needed on drawings.
Identify, explain, and accurately use the two systems of linear measurement to
dimension drawings.
Describe the difference between unidirectional and aligned dimensioning.
Identify and explain the three basic types of dimensions.
Apply the general rules for dimensioning inch and/or metric drawings.
Dimension circles, holes, arcs, and angles.
Explain the methods used in the conversion to metric dimensioning from
conventional inch dimensioning.
Describe the basic principles of geometric dimensioning and tolerancing.
Explain how dimensions are generated in computer-aided drafting.
After students have read the chapter, review it with them. Discuss the following:
The reasons a drawing must be dimensioned accurately.
The reasons notes are needed on a drawing.
Aligned and unidirectional dimensioning.
General rules for dimensioning.
The problems that might occur if an improperly dimensioned drawing is
used to manufacture an object.
The proper way to dimension circles, holes, and arcs. Refer to old and new
ASME standards.
The proper way to dimension angles.
Project a drawing that is improperly dimensioned with a jumble of lines and
dimensions. Project the same drawing properly dimensioned.

If time permits, discuss the changeover from conventional measurement to metric
measurement and the problems that can occur if not done properly.
Review the Drafting Vocabulary.
Assign the Test Your Knowledge questions as a quiz or for completion outside of
class . Assign either of the chapter quizzes provided in this resource.
Assign the problems at the end of the chapter. The number of problems assigned
and their difficulty will depend on the time available and student ability. To save
time and increase the number of problems that can be done, use the preprinted
sheets in the Exploring Drafting Worksheets.
Have students volunteer for Outside Activities assignments.
Materials: Drafting Textbook
Drafting tools
Drafting media
1. Contact several industrial drafting departments. If possible, obtain copies of the standards they
use for dimensioning. Compare how similar or dissimilar they are. Do they vary by industry?
2. Obtain copies of several industrial prints. Study how they are dimensioned and how notes are
used. Are there any provisions for foreign components to be used with the items on the prints? Will
the parts be exported?
Worksheet 10-1: Dimensioning Problems
Worksheet 10-2: Dimensioning Problems
Worksheet 10-3: Dimensioning Problems
Worksheet 10-4: Dimensioning Problems
Worksheet 10-5: Dimensioning Problems
Worksheet 10-6: Dimensioning Problems
Reproducible Master 10-1: Dimensioning Methods
Reproducible Master 10-2: Dimensioning Lines and Standards

Reproducible Master 10-3: Preferred Dimensioning Practices (Grouping and
Placement)
Reproducible Master 10-4: Preferred Dimensioning Practices (Object Description
and Extension Lines)
Reproducible Master 10-5: Metric Dimensioning Methods
Transparency 10-1: Dimensioning Hole Features
Other resource:
Other resource:
1. Test Your Knowledge Questions, Text page 246
2. Quiz 10A, Instructor's Resource CD
3. Quiz 10B, Instructor's Resource CD
4. Other assessment:
American Society of Mechanical Engineers (ASME)
www.asme.org