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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This convention may take some experience. This is how the remaining rear section would look. Isometric drawings can show overall arrangement clearly, but not the details and the dimensions.

Engineering Drawing and Sketching

When the left side of the block is “radiuses” as in figure 30, we break our rule that we should not duplicate dimensions. This cross-sectional view section A-A, figure 17one that is orthogonal to the viewing direction, shows the relationships of lengths and diameters better.

The diagonal lines on the section drawing are used to indicate the area that has been theoretically cut. This can be called the datum line of surface. An extension line extends a line on the object to the dimension line.

These lines are called section lining or cross-hatching. If the isometric drawing can show all details and all dimensions on one drawing, it is ideal. Imagine that you have an object suspended by transparent threads inside a glass box, as drwing figure 3.

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This drawing is symmetric about the horizontal enginewring. The views that reveal every detail about the object. If the drawing is made without either instruments or CAD, it is called a freehand sketch. In learning xectioning, we will approach it from the perspective of manual drafting. Lines that are not parallel to these axes will not be of their true length. 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.

NPTEL :: Mechanical Engineering – Engineering Drawing

Not only will these clutter the drawing, but if “tolerances” or accuracy levels have been included, the redundant dimensions often lead to conflicts when the tolerance allowances can be added in different ways. We have “dimensioned” the object in the isometric drawing in figure 7. This is especially true for the engineer. Original link is http: Somewhere on the paper, usually the bottom, there should be placed information on what measuring system is being used e.

Dimensioning should follow these guidelines.

The cross-section on the right of figure 22 is technically correct. We can dimension directly to the centerline, as in figure A complete engjneering of dimensions will permit only one interpretation needed to construct the part.


Then draw the object on each of three faces as seen from that direction. We chose one datum surface in figure 27, and another in figure Do not put in redundant dimensions.

One can pack a great deal of information into an isometric drawing. In order to get a more complete view of engineeriny object, an orthographic projection englneering be used. This eliminates the addition of measurement or machining inaccuracies that would come from “chain” or “series” dimensioning.

It is helpful to choose the placement of the dimension in the order drxwing which a machinist would create the part. We hope you like the object in Figure 1, because you’ll be seeing a lot of it. Seasoned engineers can interpret orthogonal drawings without needing an isometric drawing, but this takes a bit of practice. We will treat “sketching” and “drawing” as one. The spacing between lines should egnineering uniform.

In figure 29 we have shown a hole that we have chosen to dimension on the left side of the object.