12 Dec SECTIONING IN ENGG DRAWING. 1. SECTIONING; 2. Sections are used to show interior details clearly. A cutting-plane line shows. Orthographic Views & Sectioning. Prof Ahmed Kovacevic. Engineering Drawing and Design – Lecture 4. School of Engineering and Mathematical Sciences. 16 Jan The sectioning in Engineering Drawing can be done by using the following steps. 1) First, decide about the correct positioning of the cutting.

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The spacing between lines should be uniform. Extension lines begin 1.

An isometric view of an “assembled” pillow-block bearing system is shown in figure Examples of appropriate and inappropriate placing of dimensions are shown in figure We have to make some choices when we dimension a block with a notch or cutout figure The sectional view is applicable to objects like engine blocks, where the interior details are intricate and would be very difficult to understand through the use of “hidden” lines hidden lines are, by convention, dotted on an orthographic or engineerlng drawing.

We call this an “orthographic” or “multiview” drawing. In learning drafting, we will approach it from the perspective of manual drafting.

Engineering Drawing and Sketching

Before we get started on any technical drawings, let’s get a good look at this strange block from several angles. This means that it is not really required. When the left side of the block is “radiuses” as in figure 30, we break our rule that we should not duplicate dimensions.

We can also show isometric views of the pillow-block being taken apart or “disassembled” figure Imagine a plane that cuts vertically through the center of the pillow block as shown in figure Also, engnieering hidden lines on the non-sectioned part of the drawings are not needed figure 12 since they become redundant information and may clutter the drawing.


That is, the length is roughly three times the width. The first dimension line should be approximately 12 srawing 0. Do not put in redundant dimensions. We can get around this by pretending to cut the object on a plane and showing the “sectional view”. We will treat “sketching” and “drawing” as one.

An extension line extends a line on enigneering object to the dimension line. An arrowhead is approximately 3 mm long and 1 mm wide.

Dimensioning should follow these guidelines. Notice the direction of the arrows for the “A-A” cutting plane. This cross-sectional view section A-A, figure 17one that is orthogonal enfineering the viewing direction, shows the relationships of lengths and diameters better. The total length is known because the radius of the curve on the left side is given. Lines that are not parallel to these axes will not be of their true length.

We can dimension directly to the centerline, as in figure The diagonal lines on the section drawing are used to indicate the area that has been theoretically cut. One can pack a great deal of information into an isometric drawing. These drawings are easier to make than isometric drawings.

Engineering Drawing and Sketching

To prepare a drawing, one can use manual drafting instruments figure 12 or computer-aided drafting or design, or CAD. As long as we are consistent, it makes no difference. A cross-sectional view portrays a cut-away portion of the object and is another way to show hidden components in a drawlng.

This is just an introduction. Seasoned engineers can interpret orthogonal drawings without needing an isometric drawing, but this takes a bit of practice. Engineerjng is usually best to dimension from a common line or surface. There is little choice on where to engineeribg its dimensions. These lines are called section lining or cross-hatching.


Repeatedly measuring from one point to another will lead to inaccuracies. Isometric drawings can show overall arrangement clearly, but not the details and the dimensions.

In order to get a more complete view of the object, an orthographic projection may be used. With this simple object, only three dimensions are needed to describe it completely figure The circular object in figure 6 requires only two views.

This is one of a drawwing of three-dimensional views called pictorial drawings. Unfold the box figure 4 and you have sectionung three views. A half-section is a view of an object showing one-half of the view in section, as in figure 19 and Then draw the object on each of three faces as seen from that direction.

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Notice how the dimensions originate on the datum surfaces. One of the best ways to communicate one’s ideas is through some form of picture or drawing. It is an orthogonal perpendicular projection.

Original link is http: When drawn under these guidelines, the lines parallel to these three axes are at their true scale lengths. When there is limited space, a heavy black dot may be substituted for the arrows, as in figure Which views should one choose for a multiview drawing?

In figure 29 we have shown a hole that we have chosen to dimension on the left side of the object. We hope you like the object in Figure 1, because you’ll be seeing a lot of it.