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

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

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

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

Chapter 2 CAD Systems Any Questions?

Drawings Must Be Accurate Speed Legibility Neatness

Alphabet of Lines

Alphabet of Lines

Alphabet of Lines

Keeping a Sharp Edge

The Good and The Bad

Lettering

Fractions

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.

Bisecting an Angle

Transfer an Angle Line A’-B’ can be anywhere.

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

Parallel Lines at a Given Distance

Dividing a Line Into Equal Parts

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

Drawing radius in acute angle

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

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

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).

In Class Exercise Draw an arbitrary circle of radius G Choose an arbitrary point P outside but near the circle Choose an arbitrary radius R Find the circle that passes through P with a radius R and is tangent to the first circle