Engineering 22
Hand Drawing
→ Sketching
Bruce Mayer, PE
Licensed Electrical & Mechanical Engineer
BMayer@ChabotCollege.edu
Engineering 22 – Engineering Design Graphics
1
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Learning Goals
 How to use sketching as an
effective tool →
• In The Engineering Design Process
• For REAL TIME Graphical Communication
– “Table/Desk” Discussions
– “WhiteBoard” Presentations
 Use Sketching to form a 3D
visualization of objects Described by 2D
MultiView Drawing (BluePrint Reading)
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Learning Goals cont.
 List the “Tools of the Trade”
• Pencils, Paper, Erasers
 Develop Mechanical Skills for Drawing
• Plan View; i.e., “Straight-On” Sketches
• Isometric Sketches
• Oblique Sketches
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Sketching
 Definition
• A Rough Freehand Drawing Used To
Document, Communicate, And Refine
Concepts Developed Primarily In The
Ideation Phase Of The Design Process
 Follows Standard Tech Dwg Practices
 A Developed Skill → Practice Required
 Typically The First Step Of Any CAD or
Mechanical Drawing
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Communication by Sketching
 An Effective Means Of Communication
During A Group Brainstorming Session
• Understand your audience
• Who is looking at the sketches?
• What details are they interested in?
• What type of sketch will they best
understand?
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Leverage Drawing Standards
 Follow Standard Technical Drawing
Practices
• You May Not Always Accompany Your
Sketches
• Others May Misinterpret Your Drawing
 Provides a Log Of
Ideas That Were
Considered in
Creative Meetings
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Visible line
Hidden line
Hatching
Centerline
Dimension
Extension
Leader
Cutting Plane
Viewing Plane
Short break
Long break
Phantom
Stitch
Recall Std Lines
 Line Patterns
Communicate What
The Line
Represents In The
Drawing
 Line Patterns Tell
You Information
Such As Whether
The Line Is Hidden,
Visible, Or A
Centerline
Chain
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Creative Design by Sketching
 Quickly Translate Thoughts To Paper
• Do NOT Use Mechanical Tools (Ruler,
Compass, Etc.)
– Requires Practice To Be Neat And Fast
– Does Not Need To Be An Exact Representation
– Objects May Be Simplified
– Parts May Be Missing
• Avoid erasing
– As New Ideas Are Developed Make New Sketches
– Start With Light Lines And Then Darken With
Softer Lead Or Heavier Strokes
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Creative Visualization
 Sketching Stimulates Creativity And
Helps Visualization
• Sketching Ideas That Are Partially
Developed Often Aids The Design Process
 Do Not Wait Until You Have A Clear Picture Before You
Start Sketching
 Allow Yourself The Freedom To Make Mistakes
 Visualization Of The Entire Design Is
Essential But Often IMPOSSIBLE
Without the Aid Of Sketches
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Sketching Practices
 To Create Good Quality Sketches, Use The
Correct Grades Of Lead And Keep Your
Pencil Sharpened.
 Sketches Use Different Line Weights
(Thicknesses) To Show The Relative
Importance Of Different Lines.
 The OBJECT You Are Drawing Should Be
Thick And Black In The Sketch So That It
Stands Out From The Dimensions, Notes,
And Other Lines.
 The OBJECT Is The Subject Of Your Drawing
And Should Be Communicated Clearly.
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Sketching Mechanics
 Pencils
• Use a mechanical pencil (0.5/0.7 mm lead)
• Practice Using Different Pressure To
Produce Desired Linetypes; e.g.
Construction Lines
 Paper
• Square Grid Paper Is Often The Most
Useful
• Unlined paper is useful for “Blank Sheet”
Thinking
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Pencils and Lead
 Two Pencils Should be available
• 0.5 mm Lead-Width for Fine-Line Work
• 0.7 mm Lead-Width for Visible-Lines,
Lettering, and Sketching
 “HB” Lead is sufficient for all around use
• Drawings can be enhanced thru the use of
4H-6H Lead for Guide/Construction Lines
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Engr Comp Pad
 A valuable Sketch Aid
• Tremendous Help with
“Blocking In” Sketch
Objects
Sketch on
this side!
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Sketching Mechanics cont
 Eraser
• A Good Eraser Is Worth The Investment
• Do Not Overuse Your Eraser (Save Some
Mistakes)
 Good Sketching Techniques
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Sketching Straight Lines
 Mark starting and ending point
 Start With A Light Pass If Necessary And Then
Darken
 Draw Long Lines With Short Light Segments
Before Making A Continuous Dark Pass
 Use a Loose, Comfortable Grip
 Re-orient The Paper To Your Convenience
 Test Your Skill With Different Orientations
• An Awkward Orientation May
Occasionally Produce Positive Results
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Straight Lines
 Straight Lines are the FOUNDATION of
FreeHand Sketching
• Used to “Block-In” All Other Shapes
DON’T USE A STRAIGHT EDGE!
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Sketching Curved Lines
 Break large arcs/circles into small
segments
• Make at least 3 guide marks for each segment
 Circles
• Sketch a Light Square And Diagonals
• Mark 2/3 Distance Along Diagonals
• Connect Intersections
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Circle Sketching
Diameter
2/3 of center distance
PLUS SIGN
MARKS CENTER
SKETCH SQUARE
SKETCH ARCS
FOR CIRCLE
Engineering 22 – Engineering Design Graphics
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 2/3
Method
SKETCH AND MARK
DIAGONALS
DARKEN CIRCLE
Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Curved Lines cont.
 Ellipses Are DIFFICULT
• Use Block-In Method
as With Circles
– Start With Rectangle
• Start With Light Lines
– Darken When Proportions
Are Pleasing
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Scale & Proportion
 Sketches Are NOT
Usually Made To A
Particular Scale.
 It is Important To
Keep The Sketch In
PROPORTION
 Use Engr Comp Pad
Paper Or Estimate
Proportions By
Comparison
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Blocking-In is Critical
1.
 Sketch the Main Enclosing
Rectangle Construction Lines
2.
 Block-In Significant
Feature Locations
 “Fair” in Curved-Feature 3.
Construction Lines
 Dim/Lighten Construction Lines 4.
w/ Soft Eraser, then Darken
Visible Lines
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Sketches for Patent Doc.
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
USA Patent App. 20030113451
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Pictorials
 Goal
• How to represent a 3-D object effectively
on a 2-D drawing surface
 Definition:
• A Sketch Developed For Ease Of
Visualization That Shows An Object’s
Height, Width, And Depth In A Single View
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Pictorial Utility
 A Powerful Communication Tool
• Particularly Useful for Non-technical
Audiences
– NonEngineers Often Have Difficulty Visualizing
True-Length-Projection Sketches/Dwgs
• Typical Uses
– Assembly Drawings
– Marketing & Product-Promotion Discussions
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Pictorial Utility
 Helpful In The Ideation Phase Of The
Design Process
 How We Picture Objects In Our Mind
 How We Visualize
Spatial
Relationships
 A Nice
Concept
Sketch
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Pictorial Sketches - Types
 Parallel Projection
• Parallel lines are ALWAYS drawn Parallel
• Easy to draw
– But…Often appears distorted
• Two Common Types
– Oblique Pictorials
 Easiest to Draw; But Most Distorted in Depth
– Isometric Pictorials
 More “Realistic” Impression
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Pictorial Types cont.
 Perspective Projection – Special Case
• Conveys Information About Distance And
Size
• Most “Realistic” and Artistic of the Pictorial
Representations
• Most Difficult to Draw
– Not as Common As
Parallel Projection
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Oblique Sketching
 Best When Most of Information is on the
“Front” of The Part
• The Forward Facing View is a True-Length
Projection-Type Image → Curves in this View
• “Depth” Lines
– Can be Projected Backward at ANY Angle
 Perfect for Engr-Comp-Pad as Sketch Medium
– Can Appear Badly Distorted
 Full-Length Depth Images Are called “Cavalier” (without
regard) Oblique
 ½ or ¾ Depth Scale Usually Yields a More Natural Image
 Called a “Cabinet” Oblique Drawing
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Oblique Sketching
1. Start with Engineering Comp-Pad
2. Block-in Main Features Using 45° Depth Lines

Locate Block Faces at Proper Depth
3. Suggest Using Cabinet Oblique at 1/2 Scale

Depth Lines Recede at Rate of 1 Diagonal per
2 True-Length Units
4. Sketch all Arcs & Circles (Hopefully on Front-V)
5. Darken all Visible Lines
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Cabinet Oblique – 0.707 Scale
 “Guide Block”
Sketch
5 Squares
 Quickly Drawn on
Engineer Comp-Pad
 Depth Scale is 70%
2.5 Diagonals
• Technically it’s One
Depth Diagonal per
Two True-Length
Units:
Scale  2 : 2
 1: 2
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Isometric Pictorials
 Most Common
• Surfaces On All Principle Planes Distorted
– All Circles appear as ellipses
– Perpendicular Lines Drawn at 60° or 120° angles
• Height Drawn Along Vertical Axis
• Width And Depth Drawn at 30° to Horizontal
– Can Use Other Angles For Receding Lines to
Achieve More Realistic Image
 Typically About 20°
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Isometric Sketching
 Begin Drawing By Blocking In Height, Width
And Depth Of Entire Object
 Continue to Block-In Smaller Features
 Add Curved Surfaces Last
• Circles Appear As Ellipses
• Lines Tangent To Arcs Locate
The Edge Of Curved Surfaces
 Isometric Grid Paper Can Help
• Follow direction of axis and count intersections
• Use tracing paper or grid paper with light lines
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Receding Line Direction
 The Receding Line Typically “recedes” UP
and to the RIGHT
• But Any Direction of Recession is Acceptable
– UP and to LEFT is also quite often used
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Sketch Mechanics Summary
1. Learn to Sketch Straight Lines
•
Critical to Effective Sketch Communication
2. BLOCK-IN Feature Outlines using
STRAIGHT Lines
3. Draw “Decent” Circles
4. Develop a Sense for Proper Proportions
5. Emphasize IMPORTANT Features With
DARKER Lines
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
All Done for Today
Try 0.7mm
MechPencil
w/ HB or B
Lead
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Engr/Math/Physics 25
Appendix
f x   2 x  7 x 
9x  6
3
2
Bruce Mayer, PE
Licensed Electrical & Mechanical Engineer
BMayer@ChabotCollege.edu
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt
Sketch City
Engineering 22 – Engineering Design Graphics
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Bruce Mayer, PE
BMayer@ChabotCollege.edu • ENGR-22_Lec-07_Sketching.ppt