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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However, if the object in figure 2 had a hole on the back side, it would not be visible using a single isometric drawing.

Sectipning engineers can interpret orthogonal drawings without needing an isometric drawing, but this takes a bit of practice. It is helpful to choose the placement of the dimension in the order in which a machinist would create the part. This is one of a family of three-dimensional views called pictorial drawings.

The spacing between lines should be uniform. We can dimension directly to the centerline, as in figure Then draw the object on each of three faces as seen from that direction. It is often better drasing measure from one end to various points. An arrowhead is approximately 3 mm long and 1 mm wide. The lines are thin and are usually drawn at a engnieering angle to the major outline of the object.


Engineering Drawing and Sketching

However, the convention in a engineeting is to show the view on the left as the preferred method for sectioning this type of object. Which views should one choose for a multiview drawing? The representation of the object in figure 2 is called an isometric drawing. This drawing is symmetric about the horizontal centerline. The purpose of dimensioning is to provide a clear and complete description of an object.

In order to engineerinf the feel of what dimensioning is all about, we can start with a simple rectangular block. To prepare a drawing, one can use manual drafting instruments figure 12 or computer-aided drafting or design, or CAD.

Engineering Drawing and Sketching

Do not put in redundant dimensions. Also in this drawing, two holes are identical, allowing the “2x” notation to be used and the dimension to point to only one of the circles. A second, rarer, use of cross-hatching is to indicate the material of the object.

One can pack a great deal of information into an isometric drawing. Extension lines begin 1. The first dimension line should be approximately 12 mm 0.

It corresponds closely to what you actually see when viewing the object from a particular angle. This cross-sectional view section A-A, figure 17one that is orthogonal to the viewing direction, shows the relationships of lengths and diameters better. When drawn under these sectiohing, the lines parallel to these three axes are at their true scale lengths.


We can get around this by pretending to cut the object on a plane and showing the “sectional view”. Not only will these clutter the drawing, but if “tolerances” or accuracy levels have been included, the redundant dimensions engineerign lead to conflicts when the tolerance allowances can be added in different ways.

NPTEL :: Mechanical Engineering – Engineering Drawing

Examples of appropriate and inappropriate placing of dimensions are shown in figure Rngineering chain-dotted are used for symmetric objects, and also for the center of circles and holes. For example, some objects need only two views, while others need four. Draawing eliminates the addition of measurement or machining inaccuracies that would come from “chain” or “series” dimensioning.

If the isometric drawing can show all details and all dimensions on one drawing, it is ideal. Usually hidden dotted lines are not used on the cross-section unless they are needed for dimensioning purposes. We have to make some choices when we dimension a block with a notch or cutout figure Dimensioning should follow these guidelines.