Engineering Graphics
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COMPUTER-AIDED DRAFTING (CAD) and COMPUTERAIDED DESIGN AND DRAFTING (CADD): Using computer techniques with the aid of graphic data processing systems to graphically express or solve technical equations is called CAD or CADD. ENGINEERING DRAWINGS and ENGINEERING DRAFTING: Drawings used in technical work or industrial production are referred to as engineering drawings. The terms working drawings and machine drawings are also used in reference to engineering drawings. ENGINEERING GRAPHICS or ENGINEERING DESIGN GRAPHICS: Engineering graphics or engineering design graphics refers to the design and specifications for physical objects and data relationships as in engineering and science..
Line Conventions Introduction Line conventions
Centerlines The widths and construction of the lines you use in making a drawing are important to interpreting the drawing. Line configurations and the meanings assigned to these configurations are known as line conventions. Line conventions convey information as succinctly as a physical example of the object itself. The appropriate use of standard line conventions enables fabricators to replicate objects based solely on your drawing. Centerlines Lines that indicate the center of an object or shape are called centerlines. Centerlines are often the first lines drawn and serve to position images on paper. Sometimes, measurements use centerlines as a common point of reference.
Visible lines Any lines visible in a view that define edges or outlines of objects are drawn with lines referred to as visible lines. Visible lines are drawn as solid, thick lines. In drawings that do not have cutting planes, visible lines will be the thickest lines drawn.
Hidden lines
Lines not readily apparent in a view of an object are hidden lines. Hidden lines are evenly-spaced, short dashes that begin and end as a dash in contact with the line from which it starts and stops. The exception being when it is a continuation of an unbroken line.
•Extension lines
Extension lines are thin lines that extend from the object outline or point on the object to a place outside the image area. Extension lines define areas for dimensions. You should leave a 1/16" gap between the object outline or point on the object and the beginning of the extension line. Extension lines project 1/8" beyond the outermost dimension line. Extension and dimension lines are drawn at right angles to each other.
Dimension lines
Lines that define the parameters of a dimension are called dimension lines. Dimension lines are thin lines terminating in arrowheads. Place dimension lines no closer than 3/8" from the object outline. Parallel dimension lines should be a minimum of 1/4" apart. You may place parallel dimension lines more than 1/4" apart so long as the spacing between dimension lines is uniform throughout the drawing. Dimension lines are generally broken in the center of the line to provide a space for the dimension figure.
When indicating the radius of an arc or circle, place the arrowhead at the end . of the dimension line that touches the object outline. The end of the dimension line terminates at the centerline of the arc or circle.
Break lines
When an extended part of an object has a continuous shape and size, you can save space by abbreviating the object using zigzag or wavy lines. These zigzag or wavy lines are called break lines because you figuratively break away an unimportant segment of an object. The two types of break lines are long break lines and short break lines. LONG BREAK LINES: Long break lines are ruled lines with freehand zigzags that reduce the size of the drawing required to delineate an object and reduce detail. SHORT BREAK LINES: To indicate a short break in an object, use thick, solid, wavy freehand lines. Rods, tubes, and bars have additional conventions that not only break their length but also imply the material or texture of the object.
Viewing or cutting plane lines
To give a clearer view of obscure or oblique planes and interior or hidden features of an object that cannot be clearly observed in a conventional outside view. use viewing or cutting plane lines respectively. Viewing or cutting plane lines are the thickest of all lines. Viewing or cutting plane lines are solid lines. Only when the cutting plane line is offset does the line appear as thick, short dashes. VIEWING PLANE LINES: Viewing plane lines indicate the plane or planes from which a surface or several surfaces are viewed. CUTTING PLANE LINES: Cutting plane lines indicate a plane or planes exposed by cutting and removing an imaginary section of the object. The exposed plane is called the sectional view and the line used to cut the object is referred to as the cutting plane line.
Cutting plane lines, together with arrowheads and letters,
make up the cutting plane indications. Arrowheads at the end of cutting plane lines indicate the direction from which you view the section. The cutting plane may be a simple, continuous plane, or it may be offset to show the interior detail to better advantage. Identify all cutting plane indications by the use of reference letters placed at the point of the arrowheads.
Dimensions Types of dimensions Two general types of dimensions
are size dimensions and location dimensions. Size dimensions define the size of the simple geometric shapes within a part. An example of a size dimension is the diameter of a hole or the width of a slot. Location dimensions define the location of these geometric shapes in relation to each other. An example of location dimensions is how far apart holes or slots are from each other. Two ANSI approved systems indicate dimensions on drawings: the aligned dimension and the unidirectional dimension system
Various characteristics and features of parts require
unique methods of dimensioning. These special situations include diameters, radii, rounded corners and ends, round, slotted, counterbored, countersunk, and counterdrilled holes, spot-facing, and chamfers. Counterbored holes (CBORE) are holes of different depths that share concentric centers. Countersunk (CSK) and counterdrilled holes (CDRILL) are two holes drilled and at different depths that share a common center
VIEWS A view is an image that results when an observer looks
perpendicularly toward one face of an object and obtains a true view of the size and shape of that side. This one view provides only two of the three principal dimensions (width, height, and depth) of an object. You find the third dimension in an adjacent view.
Sectional views To produce a sectional view, an imaginary
plane, called the cutting plane, cuts through the object and the two halves are separated to expose the interior construction. The direction of sight may be toward the right or left half, while you disregard the portion of the object nearest the observer. Use a cutting plane line or viewing plane line to indicate the cutting plane and the direction of sight
Line Conventions Introduction Line conventions
Centerlines The widths and construction of the lines you use in making a drawing are important to interpreting the drawing. Line configurations and the meanings assigned to these configurations are known as line conventions. Line conventions convey information as succinctly as a physical example of the object itself. The appropriate use of standard line conventions enables fabricators to replicate objects based solely on your drawing. Centerlines Lines that indicate the center of an object or shape are called centerlines. Centerlines are often the first lines drawn and serve to position images on paper. Sometimes, measurements use centerlines as a common point of reference.
Visible lines Any lines visible in a view that define edges or outlines of objects are drawn with lines referred to as visible lines. Visible lines are drawn as solid, thick lines. In drawings that do not have cutting planes, visible lines will be the thickest lines drawn.
Hidden lines
Lines not readily apparent in a view of an object are hidden lines. Hidden lines are evenly-spaced, short dashes that begin and end as a dash in contact with the line from which it starts and stops. The exception being when it is a continuation of an unbroken line.
•Extension lines
Extension lines are thin lines that extend from the object outline or point on the object to a place outside the image area. Extension lines define areas for dimensions. You should leave a 1/16" gap between the object outline or point on the object and the beginning of the extension line. Extension lines project 1/8" beyond the outermost dimension line. Extension and dimension lines are drawn at right angles to each other.
Dimension lines
Lines that define the parameters of a dimension are called dimension lines. Dimension lines are thin lines terminating in arrowheads. Place dimension lines no closer than 3/8" from the object outline. Parallel dimension lines should be a minimum of 1/4" apart. You may place parallel dimension lines more than 1/4" apart so long as the spacing between dimension lines is uniform throughout the drawing. Dimension lines are generally broken in the center of the line to provide a space for the dimension figure.
When indicating the radius of an arc or circle, place the arrowhead at the end . of the dimension line that touches the object outline. The end of the dimension line terminates at the centerline of the arc or circle.
Break lines
When an extended part of an object has a continuous shape and size, you can save space by abbreviating the object using zigzag or wavy lines. These zigzag or wavy lines are called break lines because you figuratively break away an unimportant segment of an object. The two types of break lines are long break lines and short break lines. LONG BREAK LINES: Long break lines are ruled lines with freehand zigzags that reduce the size of the drawing required to delineate an object and reduce detail. SHORT BREAK LINES: To indicate a short break in an object, use thick, solid, wavy freehand lines. Rods, tubes, and bars have additional conventions that not only break their length but also imply the material or texture of the object.
Viewing or cutting plane lines
To give a clearer view of obscure or oblique planes and interior or hidden features of an object that cannot be clearly observed in a conventional outside view. use viewing or cutting plane lines respectively. Viewing or cutting plane lines are the thickest of all lines. Viewing or cutting plane lines are solid lines. Only when the cutting plane line is offset does the line appear as thick, short dashes. VIEWING PLANE LINES: Viewing plane lines indicate the plane or planes from which a surface or several surfaces are viewed. CUTTING PLANE LINES: Cutting plane lines indicate a plane or planes exposed by cutting and removing an imaginary section of the object. The exposed plane is called the sectional view and the line used to cut the object is referred to as the cutting plane line.
Cutting plane lines, together with arrowheads and letters,
make up the cutting plane indications. Arrowheads at the end of cutting plane lines indicate the direction from which you view the section. The cutting plane may be a simple, continuous plane, or it may be offset to show the interior detail to better advantage. Identify all cutting plane indications by the use of reference letters placed at the point of the arrowheads.
Dimensions Types of dimensions Two general types of dimensions
are size dimensions and location dimensions. Size dimensions define the size of the simple geometric shapes within a part. An example of a size dimension is the diameter of a hole or the width of a slot. Location dimensions define the location of these geometric shapes in relation to each other. An example of location dimensions is how far apart holes or slots are from each other. Two ANSI approved systems indicate dimensions on drawings: the aligned dimension and the unidirectional dimension system
Various characteristics and features of parts require
unique methods of dimensioning. These special situations include diameters, radii, rounded corners and ends, round, slotted, counterbored, countersunk, and counterdrilled holes, spot-facing, and chamfers. Counterbored holes (CBORE) are holes of different depths that share concentric centers. Countersunk (CSK) and counterdrilled holes (CDRILL) are two holes drilled and at different depths that share a common center
VIEWS A view is an image that results when an observer looks
perpendicularly toward one face of an object and obtains a true view of the size and shape of that side. This one view provides only two of the three principal dimensions (width, height, and depth) of an object. You find the third dimension in an adjacent view.
Sectional views To produce a sectional view, an imaginary
plane, called the cutting plane, cuts through the object and the two halves are separated to expose the interior construction. The direction of sight may be toward the right or left half, while you disregard the portion of the object nearest the observer. Use a cutting plane line or viewing plane line to indicate the cutting plane and the direction of sight
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