Introduction to Engineering Drawing

ENGINEERING DRAWING-IDWG-101

Aamir Naveed

Lecture # 2

Line Conventions

Visible Lines – solid thick lines that represent visible edges or contours

Hidden Lines – short evenly spaced dashes that depict hidden features

Section Lines – solid thin lines that indicate cut surfaces

Center Lines – alternating long and short dashes

Line Conventions

Dimensioning Dimension Lines - solid thin lines showing

dimension extent/direction Extension Lines - solid thin lines showing point

or line to which dimension applies

Cutting-Plane Lines – indicate location of cutting planes for sectional views and the viewing position for removed partial views

Break Lines – indicate only portion of object is drawn.

Sketching Sketching is a rapid, freehand method of drawing

without the use of drawing instruments.

This is not artistic sketching, but technical sketching

Emphasis will be on sketching geometric figures to represent features of objects

Medium grade pencils work best for sketching All lines should be dark enough to standout from the

page

Use very light construction lines “Box in” the rough outline of the object Darken only the lines you wish to keep Clean up the edges and rough spots

Sketching techniques

Box In Technique

Boxing in the outer dimensions is often the first step in producing a sketch

If you don’t have a ruler, you can estimate dimensions using your pencil when sketching

Always keep your pencil at arms length

Sketching Tips

Layout of drawing using your pencil for dimensional reference

Sketching Tips

Visible lines takes precedence over all other lines

Hidden lines and cutting plane lines take precedence over center lines

Center lines have lowest precedence

0.6 mm

0.3 mm

0.6 mm

Precedence of Lines

1. Visible2. Hidden3. Center

Example

Hidden Line – used to represent features that cannot be seen in the current view

Centerlines – used to represent symmetry and to mark the center of circles and the axes of cylinders, and the axes of symmetrical parts, such as cylinders and bolts

Hidden and Center Lines

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Example