Chapter 1 Orthographic Projection
An orthographic projection is a 2-D representation of a 3-D object.
An orthographic
views are used to show the true shape of features that are not parallel to any of the principle planes of projection
Auxiliary Views
____________line are used to show imaginary breaks in objects. A ___________ line is usually made up of a series of connecting arcs. The line type is continuous and the line weight is usually thick (0.5 - 0.6 mm).
Break line
Represent axes of symmetry. Long dash - short dash and thin (0.3 mm).
Center lines
Cutting plane lines are used to show where an imaginary cut has been made through the object in order to view interior features. The line type is phantom and the line weight is very thick (0.6 to 0.8 mm). Arrows are placed at both ends of the cutting plane line to indicate the direction of sight.
Cutting Plane line
Lines in order of precedence/importance are as follows
Cutting plane line Visible line Hidden line Centerline
__________ and _____________ lines are used to show the size of an object. In general, a dimension line is placed between two extension lines and is terminated by arrowheads, which indicates the direction and extent of the dimension. The line type is continuous and the line weight is thin (0.3 mm).
Dimension and Extension lines
Creating an Orthographic Projection
Draw a 45° projector off the front view.
A drawing that communicates an idea or design.
Engineering Drawing
A set of rules and guidelines that help you create an Engineering Drawing.
Engineering Graphics
Mechanical Engineers -Detailed drawing of a part that needs to be machined. Electrical Engineers -A circuit schematic. -Circuit board layout. Civil Engineers -Plans for a bridge. -Road layout.
Examples of Engineering Drawings
rounded interior corners
Fillet
The _____________ shows the most features or characteristics of the object. It usually contains the least amount of hidden lines. The front view is chosen first and the other views are based on the orientation of the front view.
Front View
The standard views used in an orthographic projection are
Front view Top view Right side view
Hidden lines represent edges and boundaries that cannot be seen. Dashed and medium thick (0.35 - 0.45 mm).
Hidden lines
represent edges and boundaries that cannot be seen. ( rule of using lines)
Hidden lines
Some lines are more important than others
Importance is indicated by line weight or thickness
perpendicular to one projection plane but inclined to others
Inclined plane
If two lines occur in the same place, the line that is considered to be the least important is omitted
Line Precedence
For example, line type and weight can answer the following questions. Is the feature visible or hidden from view? Is the line part of the object or part of a dimension? Is the line indicating symmetry?
Line type and line weight provide valuable information to the print reader.
parallel to projection plane
Normal plane
not parallel or perpendicular to any projection plane
Oblique plane
lines are used to indicate imaginary features. >alternate positions of moving parts >adjacent positions of related parts The line type is long dash - short dash - short dash and the line weight is usually thin (0.3 mm). _________ ___ ___ __________ ___ ___ ________
Phantom line
They may also be used to indicate adjacent positions of related parts Used to indicate repeated detail. They are also used to show a change in surface direction produced by fillets and rounds. Used to indicate alternate positions of moving parts.
Phantom lines
United States = 3rd angle projection Europe = 1st angle projection
Projection Symbol
Always as a line or a surface Normal plane - parallel to projection plane Inclined plane - perpendicular to one projection plane but inclined to others. Oblique plane - not parallel or perpendicular to any projection plane
Projection of planes
rounded exterior corners
Round
___________ are used to show areas that have been cut by the cutting plane. _____________ are grouped in parallel line patterns and usually drawn at a 45° angle. The line type is usually continuous and the line weight is thin (0.3 mm).
Section line
When constructing an orthographic projection, we need to include enough views to completely describe the true shape of the part. Complex part = more views Simple part = less views
Standard Views
The object is placed in a glass box. The sides of the box represent the 6 principal planes.
The Glass Box Method
aligned horizontally and share the same height dimension
The front and right side views are
__________are used to show imaginary breaks in an object
Using Break Lines
___________represent axes of symmetry. They are important for interpreting cylindrical shapes. They are also used to indicate circle of centers, and paths of motion.
Using Center Lines
The top and front views are aligned vertically and share the same width dimension. The front and right side views are aligned horizontally and share the same height dimension.
View Alignment
Line Types
Visible line Hidden line Center line Phantom line Dimension line Extension line Cutting plane line Section line Break line
______________ represent visible edges and boundaries. Continuous and thick (0.5 - 0.6 mm).
Visible lines
Rule 1: _____________ should start and end with long dashes. Rule 2: ___________ should intersect by crossing either the long dashes or the short dashes Rule 3: ___________ should extend a short distance beyond the object or feature Rule 4: _____________ may be connected within a single view to show that two or more features lie in the same plane. CAUTION! __________ should not extend through the space between views
When Creating Center Lines
Rule 1: The length of the hidden line dashes may vary slightly as the size of the drawing changes. Rule 2: Hidden lines should always begin and end with a dash, Exception: When the hidden line begins or ends at a parallel visible or hidden line.
When Creating Hidden Lines
Rule 1: Phantom lines should start and end with a long dash.
When Creating Phantom Lines
To represent true shape and size for dimensioning and visualization of surfaces and planes that are not parallel to three orthographic planes. (inclined or oblique surfaces)
Why Auxiliary views?
The top and front views are
aligned vertically and share the same width dimension.
There are four commonly used line types
continuous hidden center phantom
1) If the distance to traverse is short the series of connecting arcs is used. 2) If the distance is long the thin straight line with a jog is used.
two types of break lines
