Introduction to Geometric Construction.ppsx

Fcjrt Richie gggjrricg

1. Engineering Drawing

2. 1)Try to write a description of
this object.
2)Test your written description
by having someone attempt
to make a sketch from your
description.
Graphics Language
The word languages are inadequate for describing the
size, shape and features completely as well as
concisely.
You can easily understand that ……..

3. Graphic language in “engineering application” use
lines to represent the surfaces, edges and contours
of objects.
A drawing can be done using freehand, instruments or
computer methods.
The language is known as “drawing” or “drafting” .
Composition of Graphic Language

4. Drawing as a Language

5. The lines are sketched without using instruments other
than pencils and erasers.
Example
Freehand Drawing

6. Instruments are used to draw straight lines, circles, and
curves concisely and accurately. Thus, the drawings are
usually made to scale.
Example
Instruments Drawing

7. The drawings are usually made by commercial software such
as AutoCAD, SolidWorks etc.
Computer Drawing
Example

8. Elements of Engineering Drawing
Engineering drawing are made up of graphics language
and word language.
Graphics
language
Describe a shape
(mainly).
Word
language
Describe size, location and
specification of the object.

9. Traditional
Drawing Tools

10. T-Square
Triangles
Drawing Tools
Drawing Board

11. Mechanical Pencils
(H) grade is used to draw light
lines, (B) grade is used to draw
heavy lines and (HB) is used for
medium lines
Wooden Pencils
Pencil Eraser
Erasing Shield
Drawing Tools

12. Pencil Grading and classification
Many pencils are graded from H (for hardness) to B
(for blackness), as well as F, a letter arbitrarily chosen
to indicate midway between HB and H. (It is a
persistent myth that F stands for fine. The standard
writing pencil is graded HB
Wooden Pencil Grade
HardMediumSoft

13. Compass
needle lead
Drawing Tools
Divider

14. ProtractorFrench Curves
Drawing Tools
Drawing Templates

15. (1) (2)
(3)
(4)
Fastening Paper to Drafting Board

16. Using T square and triangles to draw lines at
different angles

17. Trimmed paper sizes from
A0 : A6
(Dimensions in millimeters)
Drawing Sheet Size
Standard sheet size
Untrimmed
size
Trimmed
size
A0880 x 1230841 x 1189
A1625 x 880 594 x 841
A2450 x 625 420 x 594
A3330 x 450 297 x 420
A4240 x 330 210 x 297
A5165 x 230 148 x 210
A6120 x 165 105 x 148
X : Y = 1: √2
Area of trimmed sheet
A0 = 1 m2

18. Drawing space
395 x 271 mm
Table
Border lines
5 mm
5 mm
5 mm
20mm
16mm
Drawing Sheet Size (A3) 420x297mm

19. Table for Preparatory Year
BENI-SUIEF UNIVERSITY
SH. NO. :BENI-SUIF UNIVERISTY
FACULY OF ENGINNERING
DRN. BY : ……………………..
SCALE 1:1
MAT. :
WT. :
CL. NO. :
S.N. : DATE : ../../...
TITLE : ………..
DIM : mm
80 mm 40 mm 40 mm 40 mm 40 mm 40 mm 115 mm

20. Designation of a scale consists of the word “SCALE” followed
by the indication of its ratio, as following table:
Size in
drawing
Actual size
:
Scale is the ratio of the size of an
element of an object shown in
the drawing to the size of the
same element of the object.
Category Recommended Scale
Full Scale 1:1
Enlarged Scale 5:1 2:1
Reduced Scale
1:2 1:5 1:10
1:20 1:50 1:100
Drawing Scale

21. Continuous thick Visible outlinesHB 0.7
Continuous thin
(straight or curved)
Dimension lines
Leader lines
Hatching lines
2H 0.35
Continuous thin (straight)
with zigzags
Cutting lines in
layouts
2H 0.35
Dashed Medium
Hidden outlines
2H 0.5
Chain thin
Center lines
Lines of symmetry
2H 0.35
Chain thin, double-dashed Cutting plane linesHB 0.7
Line Description Application
Line grade and
thickness
Basic Line Types
Continuous thin (straight)
free hand
Cutting lines in
metals
2H 0.35
1101
51

22. Dimension line
Center line
Dashed line
Hatching line
Cutting plane line
Example: Line types in engineering drawing

23. Sequence of Drawing Letters and Numbers

24. (1) (2)
125
Fold (1)
190
Fold (2)

26. 4040
35 5
315 x170
50
51

27. Applied Geometry

28. Bisect a given angle ABC
Bisect a given line AB and to
draw a perpendicular to it
BA
R > AB/2
R
R
O
C
D
A
B
C
R
R
F
θ
θ
D
E
R
Bisect a given line and a given angle

29. A
B
r
r
a)AB is the given line, and C is the given distance
b)From any two points well apart of AB, draw two arcs of
radius equal to C
c)Draw a line tangential to the two arcs to give the required
line.
C
Drawing a line Parallel to a given line (Using Compass)

30. 30
o
60
o
60
o
30
o
A B
C
DE
F
3
0
o
6
0
o
60
o
30
o
Step 2: Using a 60° set square, project lines
upwards from point A and B respectively, as
shown. Mark off AF and BC to the same
length as AB.
How to construct a regular hexagon with a given side
Step 1: Draw line AB to the given length.
Step 3: From points F and C, project with the set square to points E and D respectively,
but first mark off the side measurements to the given size.
Step 4: Complete the hexagon by drawing line ED.

31. A
B
r
2
r
2
r
2
> r
1
r
1E
F
D
a)AB is the line, and C is the
point on it
b)With center C and any radius,
describe equal arcs to cut AB
at E and F
c)From E and F describe equal
arcs to intersect at D
d)Join C and D to give the
required perpendicular
Drawing a line perpendicular to a given line at
a given point (Using Compass)
+
C

32. r
2
r
2
r
1
B
A
D
a)With C as center, draw a arc
with radius r
1 intersecting the
given line at A and B.
b)From points A and B as a
centers, Draw arcs with radius
r
2 and intersecting at point D.
c)Join CD and extend it to
intersect the given line .
Drawing a line perpendicular to a given line at
a point not on the line (Using Compass)
C+

33. C
B
A
r
1
r
1
r
2
r
2
O

34. L
4
R
L
3
R
T
2
T
1
o
R
θ = 90 L
1
L
2
θ
R
L
4
R
L
3o
R
T
1
θ < 90
L
1
L
2
θ
θ > 90
L
1
L
2
L
3
R
L
4
R
T
2
R
o
T
1
T
2
Drawing a fillet arc, with radius R, tangential to
two straight lines

35. a)Let O be the center of the given circle and P the given point
b)Join O to P.
c)Bisect OP at point A.
d)With A as center and AO as radius, draw a semicircle
intersecting the given circle at the tangent point T.
e)Draw a line PT which is the required tangent.
A
T
Drawing of a tangent to a circle from a given point
outside the circle
OP

36. R
1
A R
2
B
a)Let A and B the centers of the given circles of radii R1 and R2 respectively,
b)Join A to B and bisect AB at point O.
c)With O as center and OA as radius, draw a semicircle.
d)With center A and radius R
1
-R
2
, draw a circle intersecting the semicircle at point C.
e)Join AC and extend it to intersect the larger of the given circles at D
f)Join CB. With CB as radius and D as center plot point E on the small circle.
g)Join DE to give the required tangent.
O
D
R=OA
C E
R
1-R
2
Drawing an external tangent to two given circles
(open-belt)
Note: R
1
>R
2

37. R
2B
R
1
A
a)Let A and B the centers of the given circles of radii R
1
and R
2
respectively,
b)Join A to B and bisect AB at point O.
c)With O as center and OA as radius, draw a semicircle.
d)With center A and radius R
1
+R
2
, draw a circle intersecting the semicircle at point C.
e)Join AC to intersect the larger of the given circles at D
f)Join CB. With CB as radius and D as center mark point E on the small circle.
g)Join DE to give the required tangent.
Note: R
1
>R
2
O
D
C
E
R
1
+R
2
Drawing an external tangent to two given circles
(crossed-belt)
R=OA

38. Note: The centers of two circles and tangent point
lie on the same straight line
Tangent points
C
1
C
2
R
1
R
2
R
1 +
R
2
C
2
R
2
C
1
R
1
R
2  R
1
When circle tangent to another circle

39. R 1
+R 2
L
1
R
2
T
2
T
1
R
1
A
R
2
L
1
R
2
R
1
A
L
2
R
2
Case (1)
Case (2)
O
O
L
2
R
2
-R
1
Drawing an arc tangential to a line and a circle
T
2
T
1

40. Drawing an arc tangential to two circles
R
1
A B
R
T
1 T
2
O
R
+
R
2R
+R 1
R
2

41. Drawing an arc tangential to two circles
T
1
T
2
R
A B
R-R
2R-R
1
R
1
R
2
O

42. T
1
T
2
R
+R 2
O
A B
R
2
R
R
1
R
-
R
1

43. 90
3042
R23
R30
R
2
2
R105
Exercise (1)
R
7
5
R
8
3

44. Exercise (2)
A B
4
2
5
3
4
9
7
5
7
2
26
7
6
8
2
9
0

45. Exercise (3)