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Standard Practice for Engineering Drawings

Standard Practice for Engineering Drawings. Introduction to Mechanical Engineering Fall 2004. Created by: P.M. Larochelle. Standard Sheets. For layout designations, title blocks, revision blocks, and list of materials blocks see the front inside cover of the text. Sheet size selection:

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Standard Practice for Engineering Drawings

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  1. Standard Practice for Engineering Drawings Introduction to Mechanical Engineering Fall 2004 Created by: P.M. Larochelle

  2. Standard Sheets • For layout designations, title blocks, revision blocks, and list of materials blocks see the front inside cover of the text. • Sheet size selection: • For simple parts use small sheets • For complex parts use large sheets

  3. Standard Sheets

  4. Title Blocks • Title Blocks record important info regarding the drawing: • Part name & number • Names of the persons that: created, modified, and approved the drawing • Dates that the drawing was created & revised • Company Name • The scale of the drawing • Etc.

  5. Title Blocks

  6. Scale • The scale of the drawing is the ratio of the size of the object as drawn to the actual size. • The scale you chose depends upon both the size of the object and the sheet size. • When practical it is always preferable to show parts and assemblies at full scale (I.e. actual size).

  7. Scale • Scales are denoted by two numbers separated by a colon e.g. 1:10 • On the left is the length on the drawing • On the right is the actual length on the object • Always use integer scales • Use 3:2 instead of 1.5:1

  8. Scale • Some scales can be denoted by text • 1:1 = FULL SCALE = FULL SIZE • 1:2 = HALF SCALE = HALF SIZE • 2:1 = DOUBLE = 2x

  9. Standard Scales

  10. Geometry • A working knowledge of the fundamental principles and terminology of geometry is essential to create engineering drawings. • We will now review the basic concepts and geometric elements commonly encountered in engineering drawing.

  11. Points • A point represents a location. It has zero dimensions; no length, width, or depth. • A point is always defined by the intersection of two line segments- never by a “dot”.

  12. Lines • Euclid defined a line as “that which has length without breadth”. In Euclid’s time and for many hundreds of years thereafter any element- straight or curved that had no breadth was called a line (e.g. french curves, splines, etc.). Today, we define a line as being straight. A line represents a point and a direction. It has one dimension- length; it has no width or depth.

  13. Lines • A line has infinite length whereas a line segment is a line of finite length. • In technical drawing we are always concerned with line segments. Therefore we abbreviate the term line segment to “line”. The term “line” in technical drawing always refers to a line segment.

  14. Lines • Parallel lines are pairs of lines that share the same direction but different points. • Perpendicular lines are pairs of lines that share the same point but have orthogonal directions. In sketches you may denote two perpendicular lines with a box at their intersection- but never in drawings.

  15. Angles • An angle is formed by two intersecting lines. • The common unit of measure for angles is the degree. • There are 360 degrees in a full circle, 60 minutes in a degree, and 60 seconds in a minute. Example: 37o26’10’’ is read as “37 degrees, 26 minutes, and 10 seconds. • Alternatively, angles can be denoted by decimal degrees. Example 37.43611 (degrees).

  16. Angles • Supplementary angles sum to 180 (degrees). • Complementary angles sum to 90 (degrees). • An acute angle measures less than 90 (degrees). • An obtuse angle measures more than 90 (degrees).

  17. Triangles • A triangle is a planar figure bounded by three line segments. • The sum of the interior angles in a triangle is 180 (degrees).

  18. Polygons • A polygon is any planar figure bounded by straight lines- a triangle is a 3-sided polygon. • If the polygon has equal angles and sides then it is a regular polygon.

  19. Circles • A circle is a planar figure formed by the set of all points equidistant from a given point. • The circumference is the distance around the circle. • The radius is the distance from the points on the circle to the given point.

  20. Solids • Three-dimensional solids bounded by plane surfaces are called polyhedra. • The plane surfaces that define a polyhedra are called faces. • If the faces are regular polygons then the solid is called a regular polyhedra.

  21. Solids

  22. References • Chapters 3&4 of Modern Graphics Communication by Giesecke, Mitchell, Spencer, Hill, Dygdon, Novak, and Lockhard, 3rd edition. Prentice-Hall, 2004. • Technical Drawing by Giesecke, Mitchell, Spencer, Hill, Dygdon, and Novak, 9th edition. Macmillan, 1991.

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