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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Then draw the object on each of three faces as seen from that direction. The spacing between lines should be uniform. Original link is http: There is little choice on where to put its dimensions. Unfold the box figure 4 and you have the three views. The total length is known because the radius of the curve on the left side is given. However, the convention in a drawing is to show the view on the left as the preferred method for sectioning this type of object.

One of the best ways to communicate one’s ideas is through some form of picture or drawing. There are many times when the interior details of an object cannot be seen from the outside figure 8.

The dimensions should be sectionong on the face that describes the feature most clearly. More usually, the type of material is indicated enginerring on the drawing, making the use of different types of cross-hatching unnecessary.

When the left side of the block is “radiuses” as in figure 30, we break our rule that we should not enbineering dimensions.

The drawiny of the object in figure 2 is called an isometric drawing. Then imagine removing the material from the front of this plane, as shown in figure These drawing notes were developed by E. Before we get started on any technical drawings, let’s get a good look at this strange block from several angles. Then, for clarity, we add the overall length of 60 and we note that it is a reference REF dimension.


We cannot tell what the inside of the part looks like from this view.

Engineering Drawing and Sketching

One form of cross-hatching may be used for cast iron, another for bronze, and so forth. When there is limited space, a heavy black engkneering may be substituted for the arrows, as in figure With this simple object, only three dimensions are needed to describe it completely figure The top “outside” view of the bearing is shown in figure A half-section is a view of an object showing one-half of the view in section, as sectioniing figure 19 engineeriny 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 isometric drawing.

Notice how the dimensions originate on the datum surfaces. We can get around this by pretending to cut the object on a plane and showing the “sectional view”. Repeatedly measuring from one point to another will lead to inaccuracies.

We will treat “sketching” and “drawing” as one.

If the drawing is made without either instruments or CAD, it is called a freehand sketch. Which views should one choose for a multiview drawing?

The lines are thin and are usually drawn at a degree angle to the major outline of the object.

In an isometric drawing, the object’s vertical lines are drawn vertically, and the horizontal lines in the width and depth planes are shown at 30 degrees to the horizontal. Imagine that you have an object suspended by transparent threads inside a glass box, as in figure 3. It srctioning usually best sectiojing dimension from a common line or surface. It is an orthogonal perpendicular projection.

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Also, some 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.

This eliminates the addition of measurement or machining inaccuracies that would come from “chain” or “series” dimensioning. This allows you to see the inner components of the bearing system.

Engineering Drawing and Sketching

Centerlines chain-dotted are used for symmetric objects, and also for the center of circles and holes. This is one of a family of three-dimensional views called pictorial drawings.

If the isometric drawing can show all details and all dimensions on one drawing, it is ideal. When drawn under these guidelines, the lines parallel to these three axes are at their true scale lengths. We have to make some choices when we dimension a block with a notch or cutout figure It corresponds closely to what you engineerjng see when viewing the object from a particular angle.

As long as we are consistent, it makes no difference. Dimensioning should follow these guidelines. This drawing is symmetric about the horizontal centerline. Notice the direction of the arrows for the “A-A” cutting plane. We can also show isometric views of the pillow-block being taken apart or “disassembled” figure Seasoned engineers can interpret orthogonal drawings without needing an isometric drawing, but this takes a bit of practice.

These drawings are easier to make enginneering isometric drawings. To prepare a drawing, one can use manual drafting instruments figure 12 or computer-aided drafting or design, or CAD.