0000011535 00000 n Completeness: nothing must be left out, and nothing duplicated. This is how the remaining rear section would look. EXTENSION LINES Leave a visible gap (≈ 1 mm) from a view and start drawing an extension line. 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. Dimensioning rules is very important for drawing standards. Put in exactly as many dimensions as are necessary for the craftsperson to make it -no more, no less. Isometric drawings can show overall arrangement clearly, but not the details and the dimensions. However, if the object in figure 2 had a hole on the back side, it would not be visible using a single isometric drawing. DRAWING & DRAFTING STANDARDS AND PRACTICES Page 7 of 24 REPORT NO: REVISION: A Figure 4-4: Fully Constrained Sketch • If a sketch is created in the context of an assembly, this will cause the part to be “adaptive” (see Figure 4-5. In order to get the feel of what dimensioning is all about, we can start with a simple rectangular block. There's no signup, and no start or end dates. 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 23). To prepare a drawing, one can use manual drafting instruments (figure 12) or computer-aided drafting or design, or CAD. It starts with a summary of the general rules for the execution and structure of technical drawings. This can be called the datum line of surface. The purpose of this guide is to give you the basics of engineering sketching and drawing. Engineering Drawings are often referred to as Mechanical-, Technical- or manufacturing drawings. 0000003484 00000 n 0000019955 00000 n A leader is a thin line used to connect a dimension with a particular area (figure 24). 0000003296 00000 n to get better understanding of the designed parts. Do not put in redundant dimensions. Learn more », © 2001–2018 Introduction 4. The objective of dimensions are to convey to Manufacturing and Inspection the engineering requirements for the end item. Engineering drawings are the industry's means of communicating detailed and accurate information on how to fabricate, assemble, troubleshoot, repair, and operate a piece of equipment or a system. With this simple object, only three dimensions are needed to describe it completely (figure 26). As a general guideline to dimensioning, try to think that you would make an object and dimension it in the most useful way. Freely browse and use OCW materials at your own pace. We will treat "sketching" and "drawing" as one. When there is limited space, a heavy black dot may be substituted for the arrows, as in figure 23. Home Take away the front half (figure 10) and what you have is a full section view (figure 11). communication (technical/engineering drawing) may prove irreplaceably useful. Knowledge is your reward. Since 2003 the ISO 128 standard contains fifteen parts, which were initiated between 1996 and 2003. 0000008710 00000 n In figure 29 we have shown a hole that we have chosen to dimension on the left side of the object. Lines that are not parallel to these axes will not be of their true length. 0000004468 00000 n Selected front view should describe the part the best. %PDF-1.4 %���� When reading a Engineering drawing, one needs to communicate how the different views was taken from a three … Imagine slicing the object in the middle (figure 9): Figure 10 - Sectioning the object in figure 8. The Mechanical Engineering … A leader may also be used to indicate a note or comment about a specific area. This eliminates the addition of measurement or machining inaccuracies that would come from "chain" or "series" dimensioning. Notice how the dimensions originate on the datum surfaces. 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. Design and Manufacturing I Courses This cross-sectional view (section A-A, figure 17), one that is orthogonal to the viewing direction, shows the relationships of lengths and diameters better. Somewhere on the paper, usually the bottom, there should be placed information on what measuring system is being used (e.g. Figure 5 - A multiview drawing and its explanation. A given part can be dimensioned in many ways and although each method should yield the same requirements in practice this is rarely true. Any engineering drawing should show everything: a complete understanding of the object should be possible from the drawing. That is, the length is roughly three times the width. If the isometric drawing can show all details and all dimensions on one drawing, it is ideal. Engineering Drawings: Dimensioning A short series of lectures on Engineering Drawing as Part of ENGG1960 By Paul Briozzo . 0000004264 00000 n 0000019694 00000 n x���1 0ð4�������v�dt�y���C. Drawing is used to record objects and actions of everyday life in an easily recognizable manner. The cross-section on the right of figure 22 is technically correct. An isometric view of an "assembled" pillow-block bearing system is shown in figure 13. 0000002260 00000 n 0000019437 00000 n (We are just showing the top view). This convention may take some experience. 0000010109 00000 n This is one of a family of three-dimensional views called pictorial drawings. 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. An extension line extends a line on the object to the dimension line. 0000004225 00000 n Readability: the appropriate line quality must be used for legibility. Figure 24 - Example drawing with a leader. Then draw the object on each of three faces as seen from that direction. We don't offer credit or certification for using OCW. The Ø stands for "diameter". The cross-section looks like figure 11 when it is viewed from straight ahead. 0000004366 00000 n Sketching is a free-wheeling type of informal drawing that helps inspire the basic design of an object before advancing to the more exacting scaled drawings. Figure 4 - The creation of an orthographic multiview drawing. 3. In learning drafting, we will approach it from the perspective of manual drafting. Extension lines begin 1.5 mm from the object and extend 3 mm from the last dimension line. Size, Location ENGINEERING … A complete set of dimensions will permit only one interpretation needed to construct the part. A good rule to … Learn Engineering Drawings Read More » The difference between first angle and third angle projection systems. Unfold the box (figure 4) and you have the three views. ), Learn more at Get Started with MIT OpenCourseWare, MIT OpenCourseWare makes the materials used in the teaching of almost all of MIT's subjects available on the Web, free of charge. Figure 18 - The top "outside" view of the bearing. 0000002753 00000 n 0000017546 00000 n This is one of over 2,200 courses on OCW. Drawings need to conform to standards. We chose one datum surface in figure 27, and another in figure 28. This allows you to see the inner components of the bearing system. Figure 29 - Exampled of a dimensioned hole. To understand how to "read" a drawing it is necessary to be familiar with the standard conventions, rules, and basic symbols used on the various types of drawings. Figure 25 - Example of appropriate and inappropriate dimensioning. No enrollment or registration. We have to make some choices when we dimension a block with a notch or cutout (figure 27). » Engineering drawings should not be dependent on any language. The representation of the object in figure 2 is called an isometric drawing. 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. » 1567 0 obj <>stream Which views should one choose for a multiview drawing? Examples of appropriate and inappropriate placing of dimensions are shown in figure 25. Engineering Drawings: Dimensioning A short series of lectures on Engineering Drawing as Part of ENGG1960 By Paul Briozzo ... side of drawing and Indicated by In STAGGERED DIMENSIONS a di to in 2.4. We cannot tell what the inside of the part looks like from this view. Design Handbook: Engineering Drawing and Sketching. Figure 19 - Full and sectioned isometric views. Before we get started on any technical drawings, let's get a good look at this strange block from several angles. Do not break the lines as they cross object lines. A half-section is a view of an object showing one-half of the view in section, as in figure 19 and 20.

engineering drawing rules

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