1. Shankar Sehgal UIET, Panjab University, Chandigarh
Machine Drawing MEC-354
Shankar Sehgal
UIET, Panjab University, Chandigarh

3. Standard Abbreviations

4. Standard Abbreviations

5. Standard Abbreviations

6. Standard Abbreviations

7. Tolerances and Fits

8. Tolerances and Fits

19. Tolerances and Fits

20. Tolerances and Fits

21. Tolerances and Fits

22. Tolerancing individual dimensions

23. Tolerancing individual dimensions

24. Tolerancing individual dimensions

25. Tolerancing individual dimensions

26. Tolerancing individual dimensions

27. Fits

28. Fits

29. Fits

30. Fits

31. Fits

32. Fits

33. Shaft basis system

34. Hole basis system

35. Machining symbols

36. Machining symbol
Any machining method may be used

37. Machining symbol
Circle means: Material removal not permitted

38. Machining symbol
Bar means:
Material removal by machining is required

39. Machining symbol Milled
Any special machining characteristics are mentioned on the extra horizontal line

40. Surface finish Peak-to-valley height Reference profile Actual profile
Datum profile
Mean profile

41. Surface finish parameters
Actual profile:
It is the profile of the actual surface obtained by finishing operation
Reference profile:
It is the profile to which the irregularities of the surface are referred to. It passes through the highest point of the actual profile.

42. Surface finish parameters
Datum profile:
It is the profile, parallel to the reference profile. It passes through the lowest point B of the actual profile.
Mean profile:
It is that profile, within the sampling length chosen (L), such that the sum of the material filled areas enclosed above it by the actual profile is equal to the sum of the material-void areas enclosed below it by the profile.

43. Surface finish parameters
Peak-to-valley height:
It is the distance from the datum profile to the reference profile.
Mean roughness index:
It is the arithmetic mean of the absolute values of the heights hi between the actual and mean profiles. It is given by,

44. Surface roughness number

45. Surface finish symbols

46. Measurement of surface finish
1. Straight edge 2. Surface guage 3. Optical flat 4. Tool maker’s microscope 5. Profilometer 6. Profilograph 7. Talysurf

47. Surface finish symbols

48. Surface finish symbols

49. Surface finish symbols

50. Welding symbols

51. Elementary welding symbols

52. Elementary welding symbols

53. Elementary welding symbols

54. Supplementary welding symbols

55. Combination of elementary and supplementary welding symbols

56. Welding symbols

57. Indication of edge preparation
Dotted line is on LOWER side.
This means that LOWER plate is to be prepared
Welding symbol on continuous line (and not on dotted line).
This means that weld is to be made on arrow side (and not on the other side).

58. Weld dimensions
a = throat thickness
z = leg length

59. Welding process designations

60. Screw threads

61. Screw threads

62. Screw threads

63. Forms of screw threads
Metric screw thread

64. Forms of screw threads
Metric screw thread

65. Forms of screw threads

66. Forms of screw threads

67. Forms of screw threads

68. Forms of screw threads

69. Forms of screw threads

70. Forms of screw threads

71. Thread designation M 10 x 1.25 means M 10 means SQ 40 x 10 means
Metric thread of nominal diameter 10 mm and pitch 1.25 mm (Fine series)
M 10 means
Metric thread of nominal diameter 10 mm and pitch 1.5 mm (Coarse series)
SQ 40 x 10 means
SQuare thread of nominal diameter 40 mm and pitch 10 mm
ACME 40 x 8 means
ACME thread of nominal diameter 40 mm and pitch 8 mm
WORM 40 x 10 means
WORM thread of nominal diameter 40 mm and pitch 10 mm

72. Side mirror of Activa scooter
Left hand thread
Side mirror of Activa scooter

73. Right hand thread

74. Conventional representation of threads
Crests of threads are indicated by a continuous thick line and the roots, by a continuous thin line.
For hidden screw threads, the crests and roots are indicated by dotted lin
For threaded parts in section, hatching should be extended to the line defining the crest of the thread.
In the view from side, the threaded roots are represented by a
portion of a circle, drawn with a continuous thin line, of length approximately three-quarters of the circumference.

75. Conventional representation of threads
The limit of useful length of screw threads is represented by a continuous thick line or a dotted line, depending on its visibility. The length up to which the incomplete threads are formed beyond the useful limit, is known as a run-out. It is represented by two inclined lines.

76. Conventional representation of threads

77. Conventional representation of threads

78. Schematic representation of threaded parts - V-threads

79. Schematic representation of threaded parts - Square-threads

80. Bolted joint

81. Hexagonal nut

82. Hexagonal nut

83. Hexagonal nut

84. Hexagonal nut

85. Method of drawing hexagonal nut
1. Draw the top view by drawing a circle of diameter, W and describe a regular hexagon on it, by keeping any two parallel sides of the hexagon, horizontal. 2. Project the view from the front, and the view from side, and mark the height equal to D. 3. With radius R, draw the chamfer arc passing through the point 1 in the front face. 4. Mark points 4 and 5, lying in-line with 2 and Locate points 8,9 on the top surface, by projecting from the view from above. 6. Draw the chamfers 4–8 and 5–9. 7. Locate points 6 and 7, lying at the middle of the outer two faces. 8. Draw circular arcs passing through the points 4, 6, 2 and 3, 7, 5, after determining the radius R1 geometrically. 9. Project the view from the side and locate points 10, 11 and Mark points 13 and 14, lying at the middle of the two faces (view from the side). 11. Draw circular arcs passing through the points 10, 13, 11 and 11, 14, 12, after determining the radius R2 geometrically.

86. Hexagonal headed bolt

87. Hexagonal headed bolt with nut and washer

88. Square nut

89. Square nut

90. Square nut

91. Square headed bolt

92. Stud bolt or stud

93. Nuts

94. Screws

95. Lock nut

96. Lock nut

97. Locking by split pin

98. Locking by castle nut

99. Wile’s lock nut

100. Locking by set screw

101. Pipe fittings

102. Pipe fittings

103. Cotter Joint

104. Cotter Joint

105. Knuckle Joint

106. Knuckle Joint

107. Muff coupling

108. Muff coupling

109. Flange coupling

110. Flange coupling

111. Footstep bearing

112. Front view of footstep bearing

113. Top view of footstep bearing

114. Footstep bearing

115. Footstep bearing

116. Footstep bearing

117. Plummer block

118. Front view of plummer block

119. Top view of plummer block

120. Plummer block

121. Screw jack

122. Screw jack

123. I.C. engine piston

124. I.C. engine connecting rod

125. I.C. engine connecting rod

128. Lathe tail stock