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# Computer Aided Engineering Drawing 20ME12P DTE Karnataka

Associate Professor em Mechanical Engineering
7 de Jan de 2021
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### Computer Aided Engineering Drawing 20ME12P DTE Karnataka

1. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 1 Computer Aided Engineering Drawing (20ME12P) Unit 1-Part 01 1. a) Illustrate the elements of dimensioning with the help of a sketch. Elements of Dimensioning: For any drawing to be workable, it is necessary that all the needful dimensions should be written on it, so that all information could be used properly. For this purpose, the following elements are written down. 1. Dimension Line. 2. Extension Line. 3. Center Line. 4. Leader Line. 5. Arrow Head. 6. Numbers. 1. Dimension Line: A Dimension Line is drawn for a given dimension of an object. This line should be at a distance from 10 mm to 15 mm from the object line. For writing a dimension, this line is broken from the middle, and the dimension is written in the middle space. Alternatively, the dimension is written on it after its completion. 2H or 4H pencil is used for this purpose. 2. Extension Line: Such lines which are drawn extending from the ends of a part of a drawing so that the dimension can be written in between them are called extension lines. 2H or 4H pencil is used for this purpose. There should be a distance of 1 mm between them and the object line. 3. Center Line: Such a line is used to represent the center of a cylindrical part of a drawing. For example, a hole shaft, etc. This should be extended up to 1 mm distance from the object line. 4. Leader Line: Any note or specification is written on an object with the help of this line. This is drawn with 2H or 4H Pencil. It consists of a circle and a leader. 5. Arrow Head: This is used at the ends of a dimension and the end of a leader. The length of the arrow-head used in engineering drawing 3 mm. 6. Numbers: After the completion of any geometric shape of an object, the writing of its size is desired. Numbers are used for this purpose. The height of the number is kept 3 mm.
2. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 2 Figure: Example for Elements of Dimensioning 1. b) Illustrate the dimensioning of given common features: diameter, radius, chord, Arc and angle. i) Dimensioning diameters Circular features like cylindrical parts like shafts, pipes, rods or any other round shape are always dimensioned by indicating their diameter. The diameter is indicated by the symbol ∅. The diameters on the circular objects may be indicated in any one of the following ways as shown in fig. Note: All Dimensions are in millimeters. ii) Dimensioning Radius The curved, fillets and round figures are shown in drawings by arcs or circles. The dimensioning is done by giving radii. The measured radius is indicated by letter R. The dimension line is drawn radial with the arrowhead touching the arc. Note: All Dimensions are in millimeters.
3. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 3 iii) Dimensioning Arcs When dimensioning the length of an arc the dimension figure identified by symbol being written above the dimension. Note: All Dimensions are in millimeters. iv) Dimensioning Chords It is a linear distance between any two points of an arc. And it is dimensioned as shown in the figure. Note: All Dimensions are in millimeters. v) Dimensioning Angles The angles are dimensioned in the same manner as that of linear dimensions. Note: All Dimensions are in millimeters. 2. a) Mention the uses of the following drawing instruments. i) T-square T square is used to draw horizontal and vertical lines on drawing sheet. It made of wood or plastic and in T shape. The vertical part of T is called as blade and horizontal part of T is called as head. The edge of head is uniform level and attached to the edge of the board. The working edge is used to draw lines anywhere on the sheet by moving the instrument top to bottom. Note: Free Hand Sketch ii) Set square Set squares are used to draw lines with an angle between them. In most of the structures, 30, 45, 60 and 90-degree lines are most common. Generally, set squares are of two types. One is 45 degree set square and another one is called as 30 – 60 degree set square. Note: Free Hand Sketch
4. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 4 iii) Bow compass A small pair of compasses one leg of which carries a pencil, pen, or point, its legs being connected by a bow-shaped spring instead of by a joint. Compass is used to draw an arc or circle with known dimensions on engineering drawing. The needle tip is placed at the respected point and pencil tip is adjusted to the height at least 1mm just above the tip of the needle. The gap is nothing but the paper thickness. Note: Free Hand Sketch iv) Clinograph Clinograph is an instrument used to draw parallel lines to the inclined lines. It contains one adjustable wing or strip which can be adjusted to required angle. So, it can be termed as adjustable set square. Note: Free Hand Sketch v) Mini drafter or Drafting Machine Mini drafter is an instrument which can be used for multiple functions in drawing. It contains two arms which are adjustable to required angle and at the end of the lower arm a scale set is attached. The scale set contains two scales connected perpendicular to each which cannot be separated. This instrument is fixed to the drawing board at one edge with the help of screw provided for the drafter. Mini drafter is used for drawing horizontal lines, vertical lines, inclined lines, angles, parallel lines, perpendicular lines etc. Note: Free Hand Sketch 2. b) Mention the uses of the following drawing instruments. i) French curves French curves are made of plastic and they are in irregular shapes. Sometimes the drawing requires irregular curves or shapes or arcs which cannot be drawn using compass. Generally French curves are more suitable for small curves and for long curves splines are used. Note: Free Hand Sketch
5. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 5 ii) Protractor Protractor is used to draw and measure the angles of lines in the drawing. It is transparent and made of plastic. It is in the shape of semi-circle, and the edge of semi-circle part consists reading with one-degree accuracy. The bottom line joins the 0o to the 180o . The center of this bottom line is marked as “O” or “C” from which the angles are measured. Note: Free Hand Sketch iii)Clips The clips are used to hold the drawing sheet on the drawing board properly. Generally, 4 clips are used for any drawing sheet. Note: Free Hand Sketch iv)Erasing Shield An eraser shield is a thin sheet of stainless steel or plastic with slots and holes of different shapes. They are designed to allow erasers to be used through them to erase lines and text without removing lines close by which do not need to be (or should not be) erased. They are about the size of a business card but the shape of the slots depends on the manufacturer. Some stainless eraser shields are made of see-through steel mesh so that the sections to be erased are easy to see. Note: Free Hand Sketch vi) Drafting machine-Same as Mini Drafter
6. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 6 3. Define RF. Mention the types of scales based on RF. Representative fraction is the ratio of the length of the object represented on drawing to the actual length of the object represented. There are three types of scales depending upon the proportion it indicates as 1. Reducing scale: When the dimensions on the drawing are smaller than the actual dimensions of the object. It is represented by the scale and R.F as Scale: - 1cm=100cm or 1:100 and by R.F=1/100 (less than one) 2. Full scale: Sometimes the actual dimensions of the object will be adopted on the drawing then in that case it is represented by the scale and RF as Scale: - 1cm = 1cm or 1:1 and by R.F=1/1 (equal to one). 3. Enlarging scale: In some cases when the objects are very small like inside parts of a wrist watch, the dimensions adopted on the drawing will be bigger than the actual dimensions of the objects then in that case it is represented by scale and RF as Scale: - 10cm=1cm or 10:1 and by R.F= 10/1 (greater than one) Note: The scale or R.F of a drawing is given usually below the drawing. If the scale adopted is common for all drawings on that particular sheet, then it is given commonly for all figures under the title of sheet.
7. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 7 4. Draw the conventional representation of lines A; Continuous Thick Line: Surroundings and sides of the matters (Outlines of the Edges), End of the Screws, B; Continuous Thin line: Measure lines, Backside section lines, Implied axis lines, to state the code of the planes, at diagonal lines which are used to state plane surface, Intersection, Leader, Hatching. C; Free Hand Line: Limits of partial and interrupted views and sections D; Continuous Thin Zigzag Line: It is used when free hand lines are drawn by tools E; Dashed Thick Lines with Dots: to state the special places / surfaces this will process additionally like to coat, to harden etc. F; Dashed Thin Lines: Invisible/Hidden Lines represents an invisible edges on the on an objects. G; Chain thin: Axis lines of symmetrical drawings, In front of section planes. K; Chain Thin with Thick Ends: Cutting Plane, to draw the trace at section planes,
8. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 8 5 Draw six horizontal parallel lines of 50 mm long with 10 mm intervals (Fig 1). 6 Draw six vertical parallel lines of 50 mm length with 10 mm intervals (Fig 2) 7 Draw 45° inclined lines (Fig 3). A to B 90 mm and B to C 6o mm Note each division 10 mm
9. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 9 8 Draw the given types of lines using 0.5 range thickness of line according to the specification (Fig 4). Note: These types of Line are Hatching lines (B5): Hatching lines are the lines which are Parallel or inclined. The minimum space between these lines should be more than twice the thickness of the heaviest line in the drawing. It is recommended that these spacing should never be less than 0.5 cm that is 5 mm.
10. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 10 9 Draw the following Exercises in A4 sheet or in your Sketch book according to the dimensions (Fig 5).
11. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 11 10 Draw the pattern drawing given Figure 1, 2, 3 Note SQ stands for Square of size
12. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 12 11 a) Illustrate the elements of dimensioning with the help of a sketch. b) Illustrate the dimensioning of given common features: diameter, radius, chord, Arc and angle. Note: 11 a and b are repeated questions do not rewrite these two questions. DIMENSIONING SYSTEM AND TYPES Note: this is a theory part not required to be written in sketch book System in Dimensioning Following are the two systems of writing dimension. 1. Unidirectional Method. 2. Aligned Method. 1. Unidirectional Method: This method is mostly used in dimensioning. In this method, the whole dimension is written in the same direction in the whole drawing. This direction is generally vertical. 2. Aligned Method: In this method of dimensioning, it is written in two directions in the whole drawing. It is written upward and at the right side and is read from the bottom and right side of a drawing. Its advantage is this that the dimensions can be written in the horizontal direction which is very easy to write.
13. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 13 Types of Dimensioning 1. Chain dimensioning: It is used where the possible accumulation of tolerances does not infringe (effect) on the functional requirement of the component. Dimensioning from a common feature is used where a number of dimensions of the same direction relate to a common origin. 2. Parallel dimensioning: Dimensions of features are taken from one datum/common origin and are shown parallel to other and placed, so that the dimensional values can easily be added.
14. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 14 3. Superimposed running dimensioning (Progressive dimensioning): It is a simplified dimensioning also cumulative error is controlled. It starts from one origin with arrow heads in one direction only. This may be used where there are space limitations and where no legibility problems would occur. The origin indication is placed appropriately and the opposite ends of each dimension line shall be terminated only with an arrow head. It may be advantageous to use superimposed running dimensions in two directions. 4. Combined dimensioning: Dimensions are given in chain dimensioning and parallel dimensioning. Common feature is combined.
15. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 15 Principles of Dimensioning Note: this is a theory part not required to be written in sketch book After completing a drawing, it is necessary that its measurements and notes should be written in such a way that they can be read easily. Follow are the Principles that have been devised for this purpose. 1. The dimensions should be given on such view which illustrates the true shape and size of an object. 2. As far as possible the dimensions should be given outside a view but can be given inside as well if unavoidable. 3. All the dimensions are given in group form. Scattering of these is not correct. 4. The dimensions should be intelligibly written. 5. All the dimensions should be written parallel to the object line and the numbers should be written such that they could be read easily. 6. The dimensions should not be repeated unless necessary. 7. The unnecessary dimensions should be avoided. 8. The extension and dimension lines should not intersect in any case. 9. While giving dimension after completing a drawing, it should be kept in mind that no unit should be written with any number. 10. The numbers should be clear, legible, and intelligible. 11. The circle, arcs, and wholes should be compatible with their radius of diameter. 12. If dimensions are needed to be given in concentric circles, then try to make them on the front view and then write their dimensions. 13. The Leader Line should be used for writing dimensions of the circles which should illustrate their diameters. 14. Refrain from ambiguous and complicated dimensions.
16. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 16 12 Copy the sketch to 1:1 scale and dimension it using Aligned system. Note: фaa, фbb and фcc are the dimensions to be measured from the figure manually using scale 13 Copy the sketch to 1:1 scale and dimension it using unidirectional system with Parallel Dimensioning method. Note: фaa, фbb, фcc, фdd, фee and фff are the dimensions to be measured from the figure manually using scale 14 Copy the sketch to 1:1 scale and dimension it using Aligned system with Chain dimensioning method. Note: aa, bb, cc, dd, ee, ff, gg, hh, ii, jj and фkk are the dimensions to be measured from the figure manually using scale
17. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 17 15 Copy the sketch to 1:1 scale and dimension it using Aligned system with Parallel dimensioning method. Note: aa, bb, cc, dd, ee, ff, gg, hh, ii and jj are the dimensions to be measured from the figure manually using scale 16 Copy the sketch to 1:1 scale and dimension it using unidirectional system with Chain dimensioning method Note: aa, bb, cc, dd, ee, ff, gg, hh, ii, jj, kk, ll and mm are the dimensions to be measured from the figure manually using scale
18. Vidya Vikas Education Trust ® Viday Vikas Polytechnic College Department of Mechanical (General) Mr. THANMAY J S Be, M-Tech, H.O.D Mechanical (General), Vidya Vikas Polytechnic College, Mysore Page 18 17 Copy the sketch to 1:1 scale and dimension it using unidirectional system with Parallel dimensioning method. Note: aa, bb, cc, dd, ee, ff, gg, hh, ii and jj are the dimensions to be measured from the figure manually using scale 15 Copy the sketch as shown in figure below dimension it in a Chain and parallel dimensioning
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