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Technical Drafting
Technical Drafting
Technical Drafting
∗ The process of creating a technical drawing
BEFORE proceeding with the manufacturing of a
technical object.
∗ When drafting objects, care must be taken to draw
accurately and neatly.
∗ A RULER must be used at all times for all lines –
straight or curved.
∗ All lines should be drawn as a single line - do NOT
shade any line.
✗Shaded line✓Single line
Drawing Lines
∗ Lines on an engineering drawing signify more than just the geometry of the object and it is important that the appropriate line be is used.
Line Thickness
∗ For most engineering drawings you will require two thickness', a thick and thin line. The general recommendation are that thick lines are twice as thick as thin lines. ∗ A thick continuous line is used for visible edges and outlines.
∗ A thinner continuous line is used for leader lines, short centre lines, dimensions and projections.
Line Styles
∗ Other line styles used to clarify important features on drawings are:∗ Thin chain lines are a common feature on
engineering drawings used to indicate centre lines. Centre lines are used to identify the centre of a circle, cylindrical features, or a line of symmetry.
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Line Styles
∗ Dashed lines are used to show important hidden detail for example wall thickness and holes.
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Line Styles
Projections
∗ A projection is the representation of a 3D object on a 2D surface.
∗ Isometric Projections
∗ Multiview Projections
Isometric Projections∗ When an object is drawn so that the lines representing
its length, height, & depth form 120° angles on the paper.
∗ An isometric projection shows the object in PERSPECTIVE – it represents three dimensions of the object in a single view.
Isometric Projections
Drawing Isometric Projections
Multiview Projections
∗ Using basic lines, the drafter draws the different views of the object just as they appear from each side.
∗ Each view in a multiview projection is represented in two dimensions.
Glass Box Approach
Glass Box Approach
Glass Box Approach
Glass Box Approach
Glass Box Approach
Glass Box Approach
Multiview Projections
∗ Although a multiview projection can represent the object in its entirety, usually only the front, top and right-side views are illustrated.
∗ The great advantage a multiview projection has over an isometric projection is the ability to show greater detail without distortion.
∗ If in one of the views, details are hidden, you must indicate that using a dashed line
Multiview Projections
∗ Check out the following link for an instructive video on how to draw multiview projections:
∗ Multiview Projection #1
(http://www.wisc-online.com/Objects/ViewObject.aspx?ID=ENG19204)
Top View
Front View Right Side View
Top View
Front View
Right Side View
Hidden lines
Center line
Exploded View
∗ An exploded view drawing in which the various parts of the object are separated from one another. (Usually drawn to scale.)
∗ This type of drawing is often included in instruction leaflets describing steps for do-it-yourself assembly of an object. (ex: wheel barrow)
Engineering Drawings
∗ A general arrangement is a technical drawing showing the overall appearance of an object – NOT all the relevant information for manufacturing the parts of the object are represented. ∗ Multiview projections are suitable for this type of
drawing, because they contain many details of the object.
∗ However, a representation in an isometric projection is often added because it offers the advantage of showing the general shape of the object in a single view.
