1. Freehand Sketches

2. Examples of Sketching Technique
Freehand drawings are known as sketches and are important communication tools that engineers use frequently while designing objects
Technical sketching is the process of producing a rough preliminary drawing representing the main features of a product structure
Freehand drawings are grouped by the level of detail, structure, and restrictions employed while creating a sketch.
For example, design sketching uses less detail, structure and fewer restrictions than freehand technical illustration.

3. Good Versus Poor Technique for Drawing Lines
Technical sketching involves the use of lines to depict products.
These images contrast good and bad techniques of sketching lines.
A good line should be straight, consistent thickness and have no unintentional breaks
Poor lines are wavy, have varying thicknesses and are disconnected.

4. Orthographic Sketches
A type of technical drawing that usually shows three different two dimensional views from different perspectives.
Orthographic sketches are a type of technical drawing that usually show three different two dimensional views of an object from different perspectives. They usually shows a front view, side view and a plan view as if you are looking down at the figure)

5. Pictorial Drawing
A type of technical illustration that shows several faces of an object at once
Pictorial drawing is a type of technical illustration that shows several faces of an object at once.
Many industries such as engineering, manufacturing and repair use pictorial drawings .

6. Classifications of Sketches
There are several classifications of sketches.
Multiview or orthographic sketches use multiple two dimensional views to accurately represent the form of a 3 dimensional object.
On the other hand, axon-o-metric, oblique and perspective sketches are all considered pictorials because each shows multiple sides of the object depicted.
Axon-o-metric sketches can vary in scale based on their intended purposes but do not converge like perspective sketches do. Axonometric sketches will be explained in more detail later in this presentation.
Oblique sketches are where the longest dimension of an object or an object’s front surface is parallel to the projection plane. Both axonometric and oblique pictorial drawing are frequently used in technical documents, sales literature and maintenance manuals.
Perspective sketches use a converging projection technique. For example, they illustrate what you see when you are looking up at a skyscraper. The top of the skyscraper is much more narrow than the bottom of the tower. This type of sketch is used more from architectural drawings.

7. Axonometric Drawing Angles
Angles define the types of axonometric drawing.
When all angles of a drawing are unequal, the drawing is considered trimetric.
When 2 of the three angles are equal, the drawing is classified as a dimetric
When all three angles are equal, the drawing is said to be isometric.

8. Position of Isometric Axes
Isometric axes can be positioned in 2 ways to create different views of the same object.
Regular isometric makes it seem like you are looking down on the top of the object.
Reversed axis isometric depicts what you would see if you were looking up to the bottom of an object.

9. Isometric vs. Non-isometric Lines
Think about this object surrounded by a cube.
The lines that run parallel to lines of the cube are considered an isometric line.
Those lines are not parallel to the cube are considered non-isometric lines

10. Isometric vs Non-isometric Planes
Similar to isometric lines, isometric planes are the planes that are parallel to the planes of a surrounding cube.
Non-isometric planes are the planes in which are not parallel to the plane’s of the cube.

11. Lines in Freehand Sketches
Next we are going to cover some lines that are to be drawn within freehand sketches. Make sure to be aware as to how these lines are drawn and where they are placed in the drawing.

12. Hidden Lines
Hidden lines are used when an object has features that cannot be seen regardless of the isometric viewpoint that is taken.
Most isometric drawings will not have any hidden lines
Hidden lines are used when an object has features that cannot be seen regardless of the isometric viewpoint that is taken.
Normally, isometric drawings will not have any hidden lines. These hidden lines are omitted unless absolutely necessary to completely describe an object.

13. Center Lines
Center lines are drawn if symmetry must be shown or for dimensioning
In isometric drawings, center lines are drawn if symmetry must be shown or for dimensioning
Normally, center lines are not used on isometric drawings when it is not important.

14. Standards for Dimensions
Follow the ANSI standard through using dimension and extension lines in the same plane with lines to be dimensioned.
Dimensioned isometric drawings used for production purposes must be ANSI standard through using dimension and extension lines in the same plane with lines to be dimensioned.
Dimensioned drawings used for illustration purposes may use the aligned method.

15. Cavalier vs. Cabinet Drawings
Two common types of oblique pictorials:
Cavalier
Cabinet
The difference between the two is how the depth of the object is represented.
Moreover, Oblique drawings come in two styles: cavalier and cabinet
Cavalier drawings use a depth dimension that is at equal scale to the Width and Height dimensions. Due to how we perceive shapes, this type of drawing looks excessively deep and distorted
Cabinet drawings use a depth dimension that is only ½ the scale of the dimensions used for Width and Height dimensions. This produces a visually more pleasing, well-proportioned appearance.
Compare the appearance of the figure drawn by each method.
Notice that the front view of both drawings is the same size; it is the depth only that is changed.

16. Drawing Shapes
In freehand sketches you need to draw shapes at different angles in order to draw the different 3-D pictorials that are used in freehand sketches.

17. Sketching a Circle To sketch a circle,
Step 1. Sketch vertical, horizontal, and inclined axes
Step 2. Mark off radius units through using a ruler or other measuring device
Step 3. Connect radius points with a rough outline until you reach your desired shape. Then fill in the line with your desired weight.

18. Sketching an Ellipse To sketch an ellipse,
Step 1: sketch your vertical and horizontal axes. Make sure that both your axes are divided into two equal halves.
Step 2: lightly sketch arcs tangent to the lines that form the rectangle.
Step 3: When satisfied with the shape of the ellipse, thicken the lines to your desired width.

19. Sketching an Isometric Ellipse
To sketch an isometric ellipse
Step 1: Draw your construction line. From the construction line draw an 30 degree angle to create your isometric axis. Draw your isometric square using parallel lines.
Step 2: Draw your diagonals and mark your centerpoint.
Step 3: Draw your major axis (the horizontal axis) and your minor axis (the vertical axis). Mark the points that both the major and minor axes touch the square.
Step 4: sketch the arcs of the ellipse using the points of the major and minor axis on your square.
Step 5: once you have reached the desired shape, darken your lines to your preferred weight.

20. Boxing-In Method for Isometric Drawings
Sketching isometric drawings is much easier if you use the boxing-in method.
To use the boxing-in method
Step 1: Draw your construction line. From the construction line, divide the line in half with another line. For each half, draw an 30 degree angle from the reference line to create your isometric axis.
Step 2: lengthen your lines from your isometric axis to your desired height, length and width.
Step 3: draw the front face of your box. Draw a line from the end of your width line that is parallel too your height line. Connect this new line to the height line with a line that is parallel to the width line.
Step 4: repeat step three for your depth line. Connect the two faces to form the top face of the box
Step 5: Draw all your isometric lines (those lines that are parallel to the lines of the box.
And step 6: draw all your non-isometric lines.

21. Drawing Angles
To draw an angle in an isometric drawing, first draw an isometric box. Then locate the endpoints of the lines that form the angles through drawing the angle two dimensionally. Use that information to connect all endpoints of your angle together.

22. Irregular Curves
Irregular curves are drawn in an isometric fashion by constructing points along the curve in multiview drawings which are then located in the isometric view.
These points are then connected with an irregular curve instrument.