Basic technical mechanical drawing notes and tutorial
Basic technical mechanical drawing notes and tutorial
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Basic technical mechanical drawing notes and tutorial
Engineering Communication
The “language of industry” is drafting. Drafting is the representation of an engineer’s ideas on paper. The drawings are often referred to as line drawings. These drawings allow the engineer to show his ideas to others and provide the necessary information for others to bring the design to life when fabricating the product. There are different types of drawings that are used in industry such as isometric, orthographic, and perspective. These drawings also produce more specialized drawings such as sectional views, exploded view drawings, cutaway drawings, and assembly drawings.
Drawings are created with lines some are darker, some are lighter some are evenly spaced dashes, some have long and short dashes, some have arrows, some show sizes or dimensions, and some do not show up on the final drawings. These lines are referred to as the alphabet of lines.
A scale drawing is on one that is larger or smaller than an object by a fixed ratio. When objects are are drawn that are much larger than a sheet of drafting paper or computer screen o too small to show up the human eye without being made larger we use scale drawings. Scales are designed enlarger or shrink objects to make the drawings easy to deal with so a drawing that is ¼th scale it would be one-fourth of it size, in other words 40 feet would 10 inches on the drawing since ¼ of one inch equal 1 foot. A 4:1 scale would mean that every inch would be equal to four feet.
Source : http://www.ndetp.org/HS/HSU3DrawingTerminologyGH.doc
Web site link: http://www.ndetp.org/
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Basic technical mechanical drawing notes and tutorial
Assignment 4
Orthographic and Isometric Drawings
- Sketch what the block in the drawing below would look like if the eye could only see:
- Front of the block - eye looking directly at the front, as labeled
- Top of the block - eye looking down on the block
- Right side of the block - eye looking towards right end of the block
You have drawn in the visible lines, called object lines, which outline the shape of the object. NOW, are there any surfaces that the eye cannot see? If so, include them as hidden lines (a series of dashes) in the appropriate view, front, top or right side.
Your views must be laid out as shown on pages 12-13 of the unit. Label each view (FRONT, TOP, RIGHT).
Sketch an isometric drawing of a solid block of wood that is 30 centimeters long, by 15 centimeters wide, by 5 centimeters thick.
NOTE: Make sketches large enough for easy viewing. Print name, class and date in lower right-hand corner of work.
Assignment 5
Elements of Drawing
- Select an area which is of interest to you and create/draw a picture/drawing of a scene from that area of interest; for examples, a nature scene you enjoy, a photograph or picture you like, a crest or an emblem, etc. NOTE:
- Use an 81/2 by 11 sheet of blank paper and include as many elements and principles of design that you possibly can.
- Identify and label (with an arrow) each of the elements and/or principles you have incorporated into your work.
- Print the title you have named your work, your name, class and date in the lower right-hand corner of your worksheet.
Here are some elements you can include:
- Lines (different types)
- Shapes and shadow/hatching
- Proportion
- Scale
- Perspective
What is Computer Aided Drafting (CAD)?
Computer Aided Drafting (referred to as CAD) is using a computer and software to draw and design objects. A CAD system can be used to:
- draw and design parts for machines (mechanical drawing),
- design houses and structures (architectural drawing),
- design roads, highways and bridges (civil drawing),
- draw and design electronic circuits (schematic drawing),
- do two dimensional (2D) and three dimensional (3D) models.
Source : http://tsud.wikispaces.com/file/view/Assignment+4+and+5.doc
http://tsud.wikispaces.com/file/view/Introduction%20to%20Computer%20Aided%20Drafting%202009.doc/203932252/Introduction%20to%20Computer%20Aided%20Drafting%202009.doc
Web site link:http://tsud.wikispaces.com
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Orthographic Drawings
Representing 3-Dimensional Objects
Overview
Orthographic drawings show three different perspectives, or views, of an object: the front, side and top views (see side diagram). Each view accurately represents the size and shape of the object. Orthographic drawings are two-dimensional, and always drawn to scale, so that the drawing perfectly represents the object. The three-dimensional shape is called the isometric view; here, it would be a picture of a rectangular prism.
1) Drawing the Orthographic View
Orthographic drawings follow a set procedure:
Top View—drawn in top, left-hand corner
Front View—drawn in bottom, left-hand corner
Side View—drawn in bottom, right-hand corner
It is easiest to begin with the front view; once
Isometric View Orthographic View
be drawn as extensions of the front view.
2) Choosing an Appropriate Scale
- How does ‘scale’ effect the nature of the orthographic drawing?
- If using a standard 8½” x 11” piece of paper, what might be an appropriate scale for drawing the orthographic view of each of the following? Be sure to include units.
- the CPU of a computer
- a “rubrics cube”
- a bolt used to put a desk chair together
- your school
- What will the width, height and depth be for the following objects, given the following scale? Note: you may need to change the units to make the measurements appropriate.
Object |
Scale |
Width |
Height |
Depth |
A cube with, sides of 120 cm.
|
1:5 |
|
|
|
r = 2mm; h = 8 mm |
10:1 |
|
|
|
A square based pyramid (1 km2); height of 0.8km |
1:10 000 |
|
|
|
3) Steps to drawing the Orthographic View:
- Tape down an 8½” x 11” piece of white paper, to avoid it slipping. Be sure to use a sharp pencil, and rotate the pencil in your fingers while drawing to obtain a consistent line.
- Decide on a scale and a point of reference. Choose a point of reference on your isometric view such as the bottom left corner of the front view, so that all views are aligned properly.
- Record all actual measurements of width, height, and depth on the isometric view.
- Draw all three views (see diagram above for lay-out).
- Label the front, top, and side views as well as all dimensions.
- Remember to include a title and scale of all dimensions to the actual object on the finished drawing.
Source : http://www.tdchristian.ca/classes/math12college/Geometry/Orthographic%20Drawings.doc
Web site link: http://www.tdchristian.ca/classes/math12college/Geometry
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The “Alphabet of lines” refer to the types of lines used in drawing
Topics :
2 dimensional drawing
3 dimensional drawing
Alphabet of lines
Assembly drawing
Center line
Construction line
Cutaway drawing
Dimension line
Exploded View drawing
Extension line
Hidden line
Isometric drawing
Model
Orthographic drawing
Perspective drawing
Prototype
Ratio
Scale
Sectional View drawing
Sectional View drawing
Visible line
Basic technical mechanical drawing notes and tutorial
Three Dimensional Illustrations using Isometric and Oblique Projection
Isometric Projection
Figure 1 shows three views of a cube in orthographic projection; the phantom line indicates the original position of the cube, and the full line indicates the position after rotation about the diagonal AB. The cube has been rotated so that the angle of 45 ° between side AC1 and diagonal AB now appears to be 30° in the front elevation, C1 having been rotated to position C. It can clearly be seen in the end view that to obtain this result the angle of rotation is greater than 30°. Also, note that, although DF in the front elevation appears to be vertical, a cross check with the end elevation will confirm that the line slopes, and that point F lies to the rear of point D. However, the front elevation now shows a three dimensional view, and when taken in isolation it is known as an isometric projection.
Figure 1 - Cube in Orthographic Projection
This type of view is commonly used in pictorial presentations, for example in car and motor-cycle service manuals and model kits, where an assembly has been 'exploded' to indicate the correct order and position of the component parts. It will be noted that, in the isometric cube, line AC1 is drawn as line AC, and the length of the line is reduced.
Figure 2 shows an isometric scale, which in principle is obtained from lines at 45° and 30° to a horizontal axis. The 45° line XY is calibrated in millimetres commencing from point X, and the dimensions are projected vertically on to the line XZ. By similar triangles, all dimensions are reduced by the same amount, and isometric lengths can be measured from point X when required. The reduction in length is in the ratio
isometric length = cos 45° = 0.7071
true length cos 30° 0.8660
= 0.8165
Figure 2 - Isometric Scale
Now, to reduce the length of each line by the use of an isometric scale is an interesting academic exercise, but commercially an isometric projection would be drawn using the true dimensions and would then be enlarged or reduced to the size required.
Note that, in the isometric projection, lines AE and DB are equal in length to line AD; hence an equal reduction in length takes place along the apparent vertical and the two axes at 30° to the horizontal. Note also that the length of the diagonal AB does not change from orthographic to isometric, but that of diagonal C1D1 clearly does. When setting out an isometric projection, therefore, measurements must be made only along the isometric axes EF, DF, and GF.
Figure 3 shows a wedge, which has been produced from a solid cylinder, and dimensions A, E,and C indicate typical measurements to be taken along the principal axes when setting out the isometric projection. Any curve can be produced by plotting a succession of points in space after taking ordinates from the X, Y, and Z axes.
Figure 3 - Construction Principles for Points in Space, with Complete Solution
Figure 4(a) shows a cross-section through an extruded alloy bar: the views (b), (c), and (d) give alternative isometric presentations drawn in the three principal planes of projection. In every case, the lengths of ordinates OP, OQ, P1, and Q2, etc. are the same, but are positioned either vertically or inclined at 30° to the horizontal.
Figure 4 - Views (b), (c) and (d) are Isometric Projections of the Section in View (a)
Figure 5 shows an approximate method for the construction of isometric circles in each of the three major planes. Note the position of the points of intersection of radii RA and RB.
Figure 5 - Construction of Isometric Circles
The construction shown in Figure 5 can be used partly for producing corner radii. Figure 6 shows a small block with radiused corners together with isometric projection, which emphasises the construction to find the centres for the corner radii; this should be the first part of the drawing to be attempted. The thickness of the block is obtained from projecting back these radii a distance equal to the block thickness and at 30°. Line in those parts of the corners visible behind the front face, and complete the pictorial view by adding the connecting straight lines for the outside of the profile.
Figure 6 - Isometric Constructions for Corner Radii
In the approximate construction shown, a small inaccuracy occurs along the major axis of the ellipse, and Figure 7 shows the extent of the error in conjunction with a plotted circle. In the vast majority of applications where complete but small circles are used, for example spindles, pins, parts of nuts, bolts, and fixing holes, this error is of little importance and can be neglected.
Orthographic Projection:
Figure 19: Orthographic Projection Shows Three Basic Views.
Isometric Drawing:
Isometric drawing is a form of pictorial drawing based on lines at 30
degrees from the horizontal. Vertical lines are drawn with the aid of
the right angle of a set square, lines at 30 degrees are drawn with the
aid of a 30,60 set square.
When constructing an isometric drawing, all measurements must be
made along the isometric axes – either the vertical lines or along the
30 degree line.
Figure 20: Isometric Drawing of a
Rectangular Prism.
Source : http://www.ecollege.ie/site/liu/metalfab_notes/module6/Isometric%20and%20Oblique%20Drawing_M6_U10.doc
Web site link to visit : http://www.ecollege.ie/
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Basic technical mechanical drawing notes and tutorial
Drafting
Drafting is a highly refined form of drawing used to communicate ideas to engineers, architects, and craftspeople. In earning this badge, Scouts learn the importance of accuracy and simplicity in developing a drawing that shows precise details in a simple format.
Requirements
- Format TWO sheets of drawing paper with proper borders and title blocks—one for your manual project (see requirement 2) and one for your lettering project (see requirement 5).
- Make a rough sketch for each of your project drawings to determine the correct size of paper to format.
- Using either single-stroke vertical or slant Gothic lettering, fill in all important information in the title block sections of the formatted paper.
- Using the formatted sheet of paper you prepared for your manual project, produce a pencil drawing as it would be used for manufacturing. Fill in all title block information. The manual drawing may be any one of the following drawing types:
- Architectural: Make a scale drawing of an architectural project. The architectural drawing may be a floor plan; electrical, plumbing, or mechanical service plan; elevation plan; or landscaping plan. Use an architect's scale and show dimensions to communicate the actual size of features. Include any important notes and considerations necessary for construction.
- Mechanical: Make a scale drawing of some mechanical device or interesting object. The mechanical drawing may be of the orthographic or isometric style. Use an engineer's scale and show dimensions to communicate the actual size of features. Include any important notes and manufacturing considerations.
- Electrical: Draw a simple schematic of a radio or electronic circuit. Properly print a bill of materials including all of the major electrical components used in the circuit. Use standard drawing symbols to represent the electronic components.
- Produce a computer-aided design (CAD) drawing as it would be used in manufacturing. Fill in all title block information. The CAD drawing may be any one of the following types:
- Architectural: Make a scale drawing of an architectural project. The architectural drawing may be a floor plan; electrical, plumbing, or mechanical service plan; elevation plan; or landscaping plan. Use an architect's scale and show dimensions to communicate the actual size of features. Include any important notes and considerations necessary for construction.
- Mechanical: Make a scale drawing of some mechanical device or interesting object. The mechanical drawing may be of the orthographic or isometric style. Use an engineer's scale and show dimensions to communicate the actual size of features. Include any important notes and manufacturing considerations.
- Electrical: Draw a simple schematic of a radio or electronic circuit. Properly print a bill of materials, including all of the major electrical components used in the circuit. Use standard drawing symbols to represent the electronic components.
- Discuss with your counselor how fulfilling requirements 2 and 3 differed from each other. Tell about the benefits derived from using CAD for requirement 3. Include in your discussion the software you used as well as other software options that are available.
- Using single-stroke slant or vertical Gothic lettering (without the aid of a template or lettering guide), write a brief explanation of what you consider to be the most important benefit of using CAD in a particular industry (aerospace, electronics, manufacturing, architectural, or other). Use the experience gained in fulfilling requirements 2, 3, and 4 to support your opinion. Use the formatted sheet of paper you prepared in requirement 1 for your lettering project.
- Do ONE of the following (a or b):
- Visit a facility or industry workplace where drafting is part of the business. Ask to see an example of the work that is done there, the different drafting facilities, and the tools used.
- Find out how much of the drafting done there is manual and how much is done using CAD. If CAD is used, find out what software is used and how and why it was chosen.
- Ask about the drafting services provided. Ask who uses the designs produced in the drafting area and how those designs are used. Discuss how the professionalswho perform drafting cooperate with other individuals in the drafting area and other areas of the business.
- Ask how important the role of drafting is to producing the end product or service that this business supplies. Find out how drafting contributes to the company's end product or service.
- Using resources you find on your own such as at the library and on the Internet (with your parent's permission), learn more about the drafting trade and discuss the following with your counselor:
- The drafting tools used in the past—why and how they were used. Explain which tools are still used today and how their use has changed with the advent of new tools. Discuss which tools are being made obsolete by newer tools in the industry.
- Tell what media types were used in the past and how drawings were used, stored, and reproduced. Tell how the advent of CAD has changed the media used, and discuss how these changes affect the storage or reproduction of drawings.
- Discuss whether the types of media have changed such that there are new uses for the drawings, or other outputs, produced by designers. Briefly discuss how new media types are used in the industry today.
- Find out about three career opportunities in drafting. Pick one and find out the education, training, and experience required for this profession. Discuss this with your counselor, and explain why this profession might interest you.
Resources
- Bethune, James E. Essentials of Drafting. Prentice-Hall, 1987.
- Bethune, James E. Drafting with Computers. Prentice-Hall, 1989.
- Bethune, James E. Modern Drafting: An Introduction to CAD. Prentice-Hall, 1989.
- Bethune, James E. Modern Electronic and Electrical Drafting with Computers. Prentice-Hall, 1989.
- Earle, James H. Drafting Fundamentals. Creative Texas, 1988.
- Earle, James H. Drafting Fundamentals 2. Creative Texas, 1989.
- Feirer, John L., and John R. Linbeck. Basic Drafting. Bennet, 1978.
- Giachino, J. W., and H. J. Beukema. Engineering Technical Drafting, 4th edition. Books Demand, 1977.
- Ramsey, Charles G., and Harold R. Sleeper. Architectural Graphic Standards, 7th edition. Wiley, 1989.
- Liebing, Ralph W. Architectural Working Drawings, 3d edition. Wiley, 1990.
- Wakita, Osamu A., and Richard M. Linde. Architectural Detailing. Wiley, 1978.
Source : http://liendoanaulac.org/work/buddy_binder/Merit%20Badges/Drafting.docx
Web site link:http://liendoanaulac.org/work/buddy_binder/Merit%20Badges
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Definitions and meaning of enginnering design terms
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Basic technical mechanical drawing notes and tutorial
Exploded view isometric orthographic perspective sectional view drawing