1. Basics of Mechanical Drawing and Dimensioning ChE 126 Borrowed mostly from the Fundamentals of Engineering Honors program at Ohio State 1

2. 2 How Would You Describe This? Describe this using only words How effective is it?

3. 3 Freehand sketches Instrument drawings Computer drawings and models Three Basic Types of Technical Drawings

4. 4 Introduction to Projections Present 3-D objects with 2-D media Two Basic Categories Orthographic Pictorial

5. 5 Orthographic Projection

6. 6 Defining the Six Principal Views or Orthographic Views

7. 7 Hidden Lines – represent features that cannot be seen in the current view Centerlines – represent symmetry and mark the center of circles, the axes of cylinders, and the axes of symmetrical parts, such as bolts Hidden and Center Lines in Orthographic Projections Object Lines – represent visible features for an object

8. 8 For Example: 1. Visible 2. Hidden 3. Center

9. 9 Step 1 – Lightly Block Three Views Use very light lines for drawing in the construction lines

10. 10 Step 2 – Lightly Block Major Features Use very light lines for drawing in the construction lines Holes Arcs Cutouts

11. 11 Step 3 – Add Final Lines Use very light lines for drawing in the construction lines

12. 12 Completed Sketch

13. 13 Dimensioning Orthographic and isometric views define the shape and general features of the object Dimensioning adds information that specifies –Size of the object –Location of features (e.g. holes) –Characteristics of features (e.g. depth and diameter of hole) Dimensions also communicate the tolerance (or accuracy) required

14. 14 Units of Measure Length –English: Inches, unless otherwise stated Up to 72" Feet and inches over 72" –SI: millimeter, mm Angle –degrees, minutes, seconds Angle Dimensions

15. 15 Dimensioning Basic Shapes – Assumptions Perpendicularity Symmetry

16. 16 Dimensioning Basic Shapes Rectangular Prism

17. 17 Dimensioning Shows: ALWAYS give DIAMETER " " for full circles (360 degrees) and RADIUS "R" for arcs (less than 360 degrees) A) Size B) Location and Orientation

18. 18 General Guidelines: Clarity is the Goal Dimension Outside of View Avoid Good Practice

19. 19 General Dimensioning Guidelines Start with basic outside dimensions of the object –Height –Width –Depth Add dimension for location and size of removed features Add general and specific notes – such as tolerances

20. 20 Practice Problem How many Dimensions are needed?

21. 21 Practice Problem How many Dimensions are needed? Answer: 8