Concordia University Mechanical Engineering Drawing Mechanical - PowerPoint PPT Presentation

Concordia University Mechanical Engineering Drawing Mechanical Engineering Drawing MECH 211/M Lecture #2; Chapters 2, 3 and 4 ; p , Dr. John Cheung

Last lecture summary Last lecture summary • Third angle projection Third angle projection. • Multi ‐ view projection. • Miter line. Folding line. i li ldi li • Inclined plane. Oblique plane. Foreshortened length. True length. True surface. • Revolution of features – Minimize hidden lines ‐ less ambiguous. 2

Quiz Quiz Rounds, Fillets & Runouts Question: Match the multi-view images with the sketches below. 3

Quiz Quiz Rounds, Fillets & Runouts Question: Question: Match the multiview images with the sketches below below. Answers: a) f ) b) c c) e d) b d) b e) d f) g g) a 4

Chapter 2 Chapter 2 CAD Systems � Any Questions? 5

Drawings Must Be � Accurate � Speed � Speed � Legibility � Neatness N 6

Alphabet of Lines 7

Alphabet of Lines 8

Alphabet of Lines 9

Keeping a Sharp Edge 10

The Good and The Bad 11

Lettering 12

Fractions 13

Bisecting A Line or Arc Draw an arc using point A somewhere close to the line centre but above and below the line. Repeat for Point B and must use the same arc length. Connect the two intersection points. 14

Bisecting an Angle 15

Transfer an Angle Line A’ ‐ B’ can be anywhere . 16

Parallel Lines Parallel Lines Through a Point Given line AB and Point P. This is more accurate. The method on the right is faster. 17

Parallel Lines Parallel Lines at a Given Distance 18

Dividing a Line Dividing a Line Into Equal Parts 19

Perpendicular Line Perpendicular Line Through a Point Given three points P, E and Given line A ‐ B and Point P, Given line A ‐ B and Point P, D. To draw a circle. draw perpendicular line p p draw line from Point P draw line from Point P from Point P. perpendicular to line A ‐ B. 20

Drawing radius in acute angle 21

Drawing arc tangent to two arcs Drawing arc tangent to two arcs Largest Radius = r + R or r ‐ R 22

In Class Exercises � Create three arbitrary points but ensure not in a line (remember points are crossed ( p lines/arcs and not dots) – chord length of circle. � Find a circle that passes through all three points points � Explain WHY your method works 23

In Class Exercise � Draw a hexagon – say M20x2.5; width across flat = 30mm. � Using the enlarging technique in 4.27 to scale it to double its size (2 times) scale it to double its size (2 times). 24

In Class Exercise � Draw an arbitrary circle of radius G � Choose an arbitrary point P outside but � Choose an arbitrary point P outside but near the circle � Choose an arbitrary radius R Choose an arbitrary radius R � Find the circle that passes through P with a radius R and is tangent to the first circle di R d i h fi i l 25