Chapter 6 Basic Geometric Constructions. Section 2 Drafting Techniques and Skills. Objectives. Use manual drafting tools and methods to make geometric constructions. Use CAD commands and methods to make geometric constructions. Draw, bisect, and divide lines.
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Chapter 6 Basic Geometric Constructions Section 2Drafting Techniques and Skills
Objectives • Use manual drafting tools and methods to make geometric constructions. • Use CAD commands and methods to make geometric constructions. • Draw, bisect, and divide lines. • Construct, bisect, and transfer angles.
Objectives • Draw triangles, squares, hexagons, and octagons. • Use special techniques to construct regular polygons. • Construct circles and arcs.
Geometric Constructions • Widely used in drafting. • Based on principles of plane geometry. • Proper instruments required in manual work. • Most efficient methods should be used in CAD work.
Bisect a Line • Strike arcs using endpoints of Line EF as centers. • Use equal radii greater than one-half Line EF. • Draw Line GH through arc intersections.
Bisect a Line • Enter Line command and enter Midpoint object snap. • Pick near midpoint of Line AB. • Draw line in any direction.
Divide a Line Into a Given Number of Equal Parts • Draw vertical line at Point B (Line BC). • Place scale so that 11 equal divisions are between Point A and Line BC. • Mark points and project them parallel to Line BC on Line AB.
Divide a Line Into Proportional Parts • Draw vertical line at Point B (Line BC). • Place scale so that nine equal divisions are between Point A and Line BC. • Mark proportional divisions and project them parallel to Line BC on Line AB.
Bisect an Angle • Strike Arc D using arbitrary radius. • Strike arcs from intersections of arcs and the angle. • Draw Line AE where new arcs intersect.
Bisect an Angle • Enter Line command and pick Point A as first point. • Enter Mid Between Points object snap. • Pick Point B and then Point C to draw the bisector.
Transfer an Angle • Strike equal arcs from Points A and A. • Draw arc from Point E to intersect Point F. • Draw arc with same radius from Point E. • Draw Line AC.
Draw a Perpendicular • Lay off three equal segments on Line AB. • Strike Arc C with radius of four units and center at Point B. • Strike Arc D with radius of five units and center at Point A. • Draw perpendicular where arcs intersect.
Draw a Perpendicular • Enter Line command and activate Perpendicular object snap. • Pick near end of given line. • Specify second point of line. • Ortho mode is quicker if given line is horizontal or vertical.
Lay Out a Given Angle • Align protractor on Line AB to mark desired angle (35). • Draw line from vertex indicator (Point C) to Point D.
Lay Out a Given Angle • Enter Line command and use polar coordinatesto draw inclined line at 60. • Specify Point C as first point. • Enter @6<60 as second point. • Polar tracking and direct distance entry allow for specific distance.
Construct a Triangle with Three Sides Given • Lay off one side (Side C) and arc with radius equal to one side. • Lay off arc with radius equal to remaining side. • Draw sides.
Construct a Triangle with Three Sides Given • Draw Side C. • Draw circle with radius equal to Arc A and center at endpoint of line. • Draw circle with radius equal to Arc B intersecting first circle. • Draw remaining sides.
Construct an Equilateral Triangle • Lay off given side (Side AB). • Strike two arcs with radii equal to side and centers at Points A and B. • Draw remaining sides where arcs meet.
Construct an Equilateral Triangle • Draw Side AB. • Enter Polygon command and specify three sides. • Enter Edge option, select endpoint, and specify side length and direction.
Construct an Isosceles Triangle • If base and side lengths are known, use triangle method for three side lengths. • If two angles and one side length are known, use triangle method for two angles and included side length.
Construct a Right Triangle • If lengths of two sides forming 90 angle are known, construct perpendicular. • Join ends to form hypotenuse.
Construct a Right Triangle with Hypotenuse and One Side Given • Draw hypotenuse (Line AB). • Draw circle with midpoint of Line AB as center and radius equal to one-half Line AB. • Draw circle with radius equal to other given side. • Draw Lines AC and BC.
Construct a Square with One Side Given • Draw Side AB. • Enter Polygon command and specify four sides. • Enter Edge option, select endpoint, and specify side length and direction.
Construct a Square with Diagonal Given • Draw circle with radius equal to half of diagonal. • Draw 45 lines across center. • Join points where inclined lines intersect circle.
Construct a Square with Diagonal Given • Enter Polygon command and specify four sides. • Pick center point. • Enter Inscribed option and specify center radius as one-half the diagonal.
