# 004 by stariya

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```									DRAFTING I                                                       Summer 2003

Basic Geometric Terms
and Construction
004.
Explain geometric terms and apply geometric construction techniques

004.01
Explain selected geometric terms

004.02
Explain the procedures for drawing standard geometric constructions

004.03
Construct drawings that require geometric constructions

1
DRAFTING I                                                                          Summer 2003

UNIT IV: Basic Geometric Terms and Construction
Competency: 004.00
Explain geometric terms and apply geometric construction techniques.

Objective: 004.01
Explain selected geometric terms.

Introduction: The purpose of this unit is to give students a basic understanding of 2D and 3D
geometry related to technical drawing. Emphasis should be placed on recognizing geometry that
exists within objects for the purpose of creating solid models within the CAD software or
creating multiview drawings. This unit covers basic geometric shapes and terms and the types of
constructions necessary to create and model basic objects.

R1(102-113):R2(151-174)

A. Identify geometric shapes and terms.
1. Angle Definition
a. acute angle - An angle that measures less than 90°.
b. obtuse angle - An angle that measures more than 90°.
c. right angle - Angle that measures exactly 90°.
d. vertex - The point at which two lines of an angle meet.
2. Circle Definition
a. radius - The distance from the center of a circle to its edge.
b. diameter - The distance across a circle through its center point.
c. circumference - The distance around the edge of a circle, better know as the circles
rim.
d. concentric - Two are more circles of different sizes that share the same center point.
e. chord - Line across a circle that does not pass at the circle’s center.
f. quadrant - one fourth (quarter) of a circle.
3. Triangle Definition
a. hypotenuse - The side of a right triangle that is opposite the 90° angle.
b. equilateral - A triangle in which all three sides are of equal length and all three angles
are equal.
c. scalene - A triangle that has sides of three different lengths and angles with three
different values.
d. isosceles - A triangle in which two sides are of equal length.
e. right triangle - A triangle in which one of the angles equals 90°.

2
DRAFTING I                                                                        Summer 2003

a. square - Four equal sides and all angles equal 90.
b. rectangle - Two sides equal lengths and all angles equal 90.
c. trapezoid - Only two sides are equal length.
d. rhombus - All sides are equal length and opposite angles are equal.
e. rhomboid - Opposite sides are equal length and opposite angles are equal.
5. Regular Polygons – A closed figure in which all of the sides and angles are of equal
measure.
a. pentagon - A five sided polygon.
b. hexagon - A six sided polygon.
c. octagon - An eight sided polygon.
d. distance across flats - A measurement across the parallel sides of a polygon.
e. distance across corners - A measurement across adjacent corners of a polygon.
6. Solids
a. Prism
i. right rectangular (box)
ii. right triangular (wedge)
b. cylinder
c. cone
d. sphere
e. pyramid
f. torus
B. Define the following:
1. Terms
a. circumscribe – The process of creating a polygon that fully encloses a circle that is
tangent to all of the polygons sides.
b. inscribe – The process of creating a polygon that is fully enclosed by a circle at its
corners.
c. bisect - Divide into two equal parts.
d. tangent - A line and arc, or two arcs that touch each other at one point only.
e. parallel - Two or more lines that are always the same distance apart.
f. perpendicular - At a 90° angle.
2. Geometric Shorthand Symbols Used by Drafters.

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DRAFTING I                                   Summer 2003

a.  (angle)
b.  (triangle)
d. Ø (diameter) Greek letter Phi
e. // (parallel)
f.  (perpendicular)
g.     (square )
h. c (centerline)
C

4
DRAFTING I                                                             Summer 2003

UNIT IV: Basic Geometric Terms and Construction
Competency: 004.00
Explain geometric terms and apply geometric construction techniques.

Objective: 004.02
Demonstrate the procedures for drawing standard geometric constructions.

R1(105):R2(154-172)

Perform the following constructions:
A. Bisect
1. lines and arcs
2. angles
B. Construct the following polygons:
1. hexagon - Across the flats (circumscribe method)
Across the corners (inscribe method)
2. octagon - Across the flats (circumscribe method)
Across the corners (inscribe method)
C. Construct arcs tangent to:
1. two arcs
2. an acute angle, right angle, and an obtuse angle
3. a straight line and an arc
D. Divide a line into equal parts

5
DRAFTING I                                                                    Summer 2003

UNIT IV: Basic Geometric Terms and Construction
Competency: 004.00
Explain geometric terms and apply geometric construction techniques.

Objective: 004.03
Construct drawings that require geometric constructions.

Requirements: Each student is required to create a geometric construction.
1. Using the drafting equipment provided, make a mechanical drawing of the object shown
below.
2. The drawing should be done at a scale of 1:1 (full size) using the measurements provided.
3. Center the drawing on the sheet.
4. Use accepted drafting standards for lines and freehand lettering.
5. Letter your name, problem number (004.03.001), scale, and date in the title block.
6. Time Limit = 90 minutes.
7. Your work will be evaluated on the accuracy of your measurements, the quality of your line
work/lettering, and your centering of the drawing.

Assessment: The geometric construction should be evaluated based on the following criteria:
Constructions correctly formed                              50 points
Accuracy                                                    25 points
Line weight, technique and neatness                         15 points
Lettering                                                   10 points

6
DRAFTING I                                                                      Summer 2003

Rubric for BASIC GEOMETRIC TERMS & CONSTRUCTIONS
Construct drawings that require geometric constructions - 004.03

Constructions correctly formed
Centers of arcs are not    Most centers of arcs are     Tangent arcs have center
located. Points of         located correctly. Most      points accurately located.
tangency are not located.  points of tangency are       Points of tangency for
Points of tangency are not located. Most points of      tangent arcs accurately
used to located start and  tangency are used to         located. Tangent arcs start    Total
stops for lines and arcs.  locate the start and stops   and stop at points of          Points
Polygons are not drawn     for lines and arcs.          tangency. Polygons drawn
using the correct method                                using the appropriate
(flats or corners) and the                              method for the size given
correct size.                                           (flats or corners).
0-35 points               36-45 points                 46-50 points

Accuracy
Numerous errors in           No more than one or two    When measured, the sizes
measurements.                errors in measurement.     of features and their
Total
Inappropriate scale used.                               locations agree with the
Points
given problem. Scale is
correct.
0-17 points                 18-23 points                24-25 points

Line weight/technique/neatness
Line weights are not        Some lines are not          Line quality is neat, clean,
uniform. Numerous           uniform. Some               well-formed, and meets
double lines. Intersections intersections are not       ANSI standards for
are not correctly formed.   formed correctly. Some      thickness, darkness, and       Total
Construction lines are too lines do not meet ANSI       coding.                        Points
dark. ANSI standards for standards.
thickness and darkness
not followed.
0-10 points                11-13 points                14-15 points

Lettering
Letter height, thickness,    Some letters are not       Lettering is neat, uniform,
and spacing are not          uniform in height,         and correctly formed and
uniform. Letters are not     thickness, and spacing.    spaced. Spelling is
Total
uniformly vertical or        Some letters are not       correct. All required
Points
inclined. Several spelling   uniformly vertical or      information is provided.
errors.                      inclined. No more than
one spelling error.
0-7 points                   8-9 points                  10 points

Total Score

7

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