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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An isometric view of an “assembled” pillow-block bearing system is shown in figure Dimensioning should follow these guidelines.
It is usually best to dimension from a common line or surface. The sectional view is applicable to objects like engine blocks, where the interior sectionnig 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.
The dimension line is a thin line, broken in the middle to allow the placement of the dimension value, with arrowheads at each end figure This drawing is symmetric about the horizontal centerline. Which views should one choose for a multiview drawing? A cross-sectional view engjneering a cut-away portion of the object and is another way to show hidden components in a device.
This is one of a family of three-dimensional views called pictorial drawings. In figure 29 we have shown a hole that we have chosen to dimension on the left side of the object.
Notice the direction of the arrows for the “A-A” cutting plane.
Also, some hidden lines on the non-sectioned part of the drawings are not needed figure 12 since they become redundant enfineering and may clutter the drawing. These lines are called section lining or cross-hatching. Then imagine removing the material from the front of this plane, as shown in secioning Before we get started on any technical drawings, let’s get a good look at this strange block from several angles. This allows you to see the inner components of the bearing system.
Extension lines begin 1. The top “outside” view of the bearing is shown in figure We cannot tell what the inside of the part looks like from this view.
One can pack a great deal of information into an isometric drawing. For example, some objects need only two views, while others need four. It corresponds closely to sedtioning you actually see when viewing sectipning object from a particular angle. The lines are thin and are usually drawn at a degree angle to the major outline of the object. A half-section is a view of an object showing one-half of the view in section, as in figure 19 and We chose one datum surface in figure 27, and another in figure One form of cross-hatching may be used for cast iron, another for bronze, and so forth.
With this simple object, only three dimensions are needed to describe it completely figure It engoneering helpful to choose the placement of the dimension in the order in which a machinist would create the part.
Engineering Drawing and Sketching
The basic drawing standards and conventions are the same regardless of what design tool you use to make the drawings. We are enfineering showing the top view.
As long as we are consistent, it makes no difference. There is little choice on where to put its dimensions. The diagonal lines on the section drawing are used to indicate the area that has been theoretically cut. When the left side of the block is “radiuses” as in figure 30, we break our rule that we should not duplicate dimensions.
A second, rarer, use of cross-hatching is to indicate the material of the object. An extension line extends a line on the object to the dimension line. Isometric drawings can show overall arrangement clearly, but not the details and the dimensions. We can dimension directly to the centerline, as in figure We can get around this by pretending to cut the object on a plane and showing the “sectional view”. Any engineering drawing should show everything: This is just an introduction.
Don’t worry about understanding every detail right now – just get a general feel for the language of graphics. Three views are not always necessary; we need only as many views as are required to describe the object sectioningg. The purpose of dimensioning is to provide a clear and complete description of an object. When there is limited space, a heavy black dot may be substituted for the arrows, as in figure Seasoned engineers can interpret orthogonal drawings without needing an isometric drawing, but this takes a bit of practice.
We hope you like the object in Figure 1, because you’ll be seeing a lot of it.