Assembly and Details 291

17.3 ASSEMBLY DRAWINGS

The assembly drawing show the relative positions of various parts grouped together in such a way that
as a whole they perform some function. Following points should be considered while preparing the
assembly drawings.
1. Choose a proper scale so as to view the drawing on the drawing sheet.
2. Two views of assembly should be drawn and when it requires more clarification then more views
should be drawn.
3. In case of symmetrical view, half views may be drawn if space is a constraint.
4. In order to observe the internal features, one or more views should be drawn in section.
5. In order to avoid the confusion on dotted line when crowding of dotted lines occurs, only few dotted
lines should be shown.
6. External threaded parts are always shown covering internally threaded parts and are not hidden by
them.
7. Overall dimensions should be shown in the assembly drawing.
8. Part list should be prepared by the serial numbers of the parts.
9. Tittle of the assembly drawing is to be written below the views.
Procedure to draw assembly drawing:
1. Study and visualize the various parts for their function, shape and size.
2. Study the relative position of parts is to be decided.
3. For sectional front view, imagine the sectional front view of all the parts.
4. Redraw the front views of all the parts in proper position and omit the overlapping or hidden lines.
5. For side view, redraw the side views of all the parts in their proper position.
6. Dark or visible lines should be decided by starting the drawing with the nearest surface and ending
with the farthest surface.

17.4 ENGINE PARTS

17.4.1 Cross Head

A crosshead is a mechanism used in long reciprocating engines and reciprocating compressors to
eliminate sideways pressure on the piston. Also, the crosshead enables the connecting rod to freely move
outside the cylinder. Because of the very small bore-to-stroke ratio on such engines, the connecting rod
would hit the cylinder walls and block the engine from rotating if the piston was attached directly to the
connecting rod like on trunk engines. Therefore, the longitudinal dimension of the crosshead must be
matched to the stroke of the engine.
Problem 1. The details of cross head are shown in Fig. 17.1. Draw the half sectional front and side view
of the assembly. Also prepared the bill of material.
Solution:
Following steps should be followed for drawing the assembly of cross head after the careful study
and visualisation of the parts for their shapes and sizes.
292 Machine Drawing

Rod end 1-off Cross head body Cap

2 1  24, 2 Holes 3
forged steel 1. off cast steel 1-Off
64 f7 64 f7 64 f7 28
32 75
Sung  24
slot 2 Holes

R85
33
R3

108
5

70H7
44 H7

44 h6
108
 44

108

28

R85
8 6
R 20
5
R8

150
R10
50 75 50
End view Half sect. R20 R20 End view Elev.
elev.

25
100 175
End view Half sect. elev.

Round head bolt (M.S) Brasses in 2 Halves 45

5 4
Gun Metal
18 24 18
2 off

70 h6
 42

24

90
R25
Snug
3×3 52 R35
35
180 8 64 H8 8
Half. Sect. Elev.

Fig. 17.1. Details of cross head

(a) The three dimensional view of assembly of cross head along the position of parts is shown in the
Fig. 17.2 and the assemble view is as shown in Fig. 17.3 along with part number.
(b) The projection provided on cross head body size 44 × 6 mm fits accurately in the corresponding
recess in the rod end of size 44 × 8 mm.
(c) The circular portion of the brasses with radius R 35 fits in the circular portion of the cross head
body.
(d) The distance between the centres of the holes in the rod end, cross head body and the cap is
108 mm and the diameter of the holes is 24 mm. The diameter of the cylindrical headed bolt is
also 24 mm. Therefore, the bolt must pass through the holes provided in the above mentioned
parts. Nuts are tightened to hold the parts together.
(e) The snug 3 mm × 3 mm provided on the cylindrical headed bolts fits in the snug slot made in the
rod end.
(f) The relative fitting position of the spigot 44 × 6 mm provided on the cross head body is to be
inserted in the corresponding recess in the rod end.
(g) The brasses are in two parts are to be housed in the cross head body and the cap.
(h) The bolts of diameter 24 mm are inserted through the holes which is having centre distance
108 mm provided in the rod end, cross head body and the cap.
(i) The nuts are tightened.
Assembly and Details 293

6
7
5
3

2
4

Fig. 17.2. The exploded view of Fig. 17.3. Three dimensional view
cross head assembly of cross head assembly

(j) The half sectional front view as given in the problem is to be redraw in their proper fitting positions.
Overlapping or hidden lines are to be omitted and complete the half sectional front view as shown
in Fig. 17.4.
(k) For drawing the side view of the assembly, redraw the side views of all the parts in their proper
position and again overlapping or hidden lines being omitted. Complete the view as shown in
Fig. 17.4.
64 H8/f7
Snug slot
33
R85

8
 42

 24

70 H7/h6
24 18
 44

44 H7/h6

0H
7
108

5
5
R3

45

R20 6
10

28 7
45
R85

R10
18 32 75 28
50
150

50
R20
25

100 175

Fig. 17.4. Two views of cross head assembly

 294 Machine Drawing

Bill of Material
S.N. Name Material No. Required

1. Cross Head Body Cast Steel 1

2. Rod end Forged Steel 1

3. Cap Cast Iron 1

4. Brasses ( in two halves) Gun Metal 1

5. Bolt Mild Steel 2

6. Nuts Mild Steel 2

7. Lock Nuts Mild Steel 2

17.4.2 Crank Shaft and Flywheel

Problem 2. The details of crank shaft and flywheel shown in Fig. 17.5. Draw the assembly. Also prepared
the part list and fit chart.
88
7
0k
5
 660

100
92

35
22

18

23 Oil holes on
Crank pin all bearings
2. Flywheel Flang to connect
O/P pulley 35H8 45H7 45H7 100H8
C.I. –1 off 35H8
62
 50 h7

M28  3
100

40
 50 h7
 120

140

40
45h7

Flywheel here
35H8 35H8
16 22
12 ,4 HOLES, Main bearing 25 22 22 25 22 145 20
EQUI. SPACED Journal Crank web 1. Crank shaft
steel–1 off

Fig. 17.5. Details of crank shaft and flywheel

 Assembly and Details 295

Tolerance Chart

35 H8 = + 0.039 45 h7 = – 0.000
+ 0.000 + 0.025

50 h7 = – 0.000 45 H7 = – 0.000
– 0.025 – 0.021

50 k7 = + 0.020 50 H7 = + 0.030
+ 0.002 + 0.000
Solution:
1. The general arrangement of crank shaft and flywheel is shown in Fig. 17.6 just to understand the
position of parts. (It is not expected as per the examination point of view)
2. The assembly of Crank Shaft and Flywheel is shown in Fig. 17.7. The part list along with fit chart
also given. (This is expected as a solution to the problem as per the Examination point of view.)
Main  120
Bearing  50h7  45h7 Main Bearing journal
journal 35
H8
 50h7
 45h7 45
H7
 45h7
Oil hole for
35 all bearing
H8

45
H7 Fly
22 10 wheel
6 0H M28  3
62 8 20
22
40

25

4, 12 EQUI. 22
35
SP. to H8
22
connect pully
25
Crank 35
H8
web
Flang to  45h7
connect out 5R for inner  50h7
put pulley common to all web

Crank shaft
Main bearing journal

Fig. 17.6. General arrangement of crank shaft and flywheel

296 Machine Drawing

A
88

B 2

A A
A
1 A
B
A

50H7/k7
35H8 35H8

M283
62 45H7 100H8

50H7/k7
120

16 22 20
35H8 35H8
25 22 22 25 22 145

C C

Fig. 17.7. Assembly of crank shaft and flywheel

PART LIST

Part No. Part Name Material Quantity

1 Crank Shaft Steel 1

2 Flywheel Cast Iron 1

FIT CHART

50 H7/k7 Interference Fit

17.4.3 Petrol Engine Piston

Problem 3. Figure 17.8 shows the details of petrol engine piston and connecting rod. Draw the assembly.
Also prepared the part list and fit chart.
Assembly and Details 297
Ring grooves for
Gudgeon pin  82 Space for scraper ring compression
bearings rings 2  3.5 C.I.
 72 R26 R6

15°
2
 20H7

45
°
TURN  64.5
0.5

29
45

24
19

17

19

16
°

87

 28
4
8

17.5

38
16

10 2
M 40 Webs
4 Thick
4

 72
4. Castle nut  67
M.S. –2 OFF  73
1. Petrol engine piston
Alluminiuam alloy–1 OFF  75
24  76.8
2

R18
 81.6
5
 20H7

5
32

1 20
1 5

8
C D 5 8
14
R
4

 10
6
R

1
1
6

58
14

6 6
M10

18
5
14 Section-CD
6
5
128

1 14
1
Section-EF
White metal
33 20
lining
36

R2 R27
0


R1 0
R

E F
6

12

3. Big–end bolt
43

M.S. –2 OFF
1
 52

 54

4
1

 44  40
2 mm Thick

4
4
 52

 54

16
Shim

10 80
12

 20g6
 10

20 R1
R28
4 36 4 CRS 56
2. Connecting rod 5. Gudgeon pin
Forged steel–1 OFF Hardened steel–2 OFF

Fig. 17.8. Details of petrol engine piston and connecting rod

298 Machine Drawing

Tolerance Chart

20 H7 = + 0.021 20 g6 = – 0.007
+ 0.000 – 0.020

Solution:
1. The general arrangement of Petrol Engine Piston and Connecting rod as shown in Fig. 17.9.
2. The assembly of Petrol Engine Piston and Connecting rod is as shown in Fig. 17.10. The part list
along with fit chart also given.

Piston

Big–End Bolt

Connecting rod

Fig. 17.9. General arrangement of petrol engine piston and connecting rod
Assembly and Details 299

A A 1
A Ring grooves for
Space for compression
 82 5 scraper ring rings 2  3.5 C.I.
Gudgeon pin  75
bearings R6
24 R26

15°

45
2

Turn  64.5

°
R18
29
24
19

19

16
17
87

32

20
17.5

38
 20H7/g6
 10
16

R
4
R

40 Webs
4

4 Thick
72
 67
14

128
 73
2 6
 75

White metal
lining 33 20
R2
0
R27
0
R1
R
6

12
43

4
52

3
32

16  10 R28

20 4
R11
4 36 4
CRS 56

Fig. 17.10. Assembly of petrol engine piston and connecting rod

PART LIST
Part No. Part Name Material Quantity
1 Piston Alloy Steel 1
2 Connecting Rod Forged Steel 1
3 Big-end Bolt Mild Steel 2
4 Castle Nut Mild Steel 2
5 Gudgeon Pin Hardened Steel 1
300 Machine Drawing

FIT CHART

20 H7/g6 Clearance Fit

17.4.4 Stuffing Box

Problem 4. Figure 17.11 shows the details of Stuffing Box. Draw the assembly. All the dimensions are
in MM.

Fig. 17.11. Details of stuffing box

Solution:
1. The general arrangement of Stuffing Box as shown in Fig. 17.12.
 Assembly and Details 301

2. The assembly of Stuffing Box is as shown in Fig. 17.13. The part list also shown.
4
5

5 3

5
2
4

Section A-A

Fig. 17.12. General arrangement of stuffing box Fig. 17.13. Assembly of stuffing box

Part List
S.N. Part Name Description Material No. Required
1. 1 Body Cast Iron 1

2. 2 Gland Brass 1
3. 3 Bush Brass 1
4. 4 Stud Mild Steel 2
5. 5 Nut M12 Mild Steel 2

17.5 BEARINGS
A bearing is a machine element that constrains relative motion to only the desired motion, and reduces
friction between moving parts. The design of the bearing may prevent a motion by controlling the normal
forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction.
Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions
of the loads (forces) applied to the parts.

17.5.1 Foot Step Bearing

Problem 5. The Fig. 17.14 shows details of foot step bearing. Draw the assembly. Also prepared the bill
of material along with fit chart.
Tolerance Chart
68 H7 = + 0.030 68 h6 = – 0.019
+ 0.000 – 0.000
50 H8 = + 0.039 50 e8 = – 0.050
+ 0.000 – 0.089
8 H7 = + 0.015 8 g6 = – 0.005
+ 0.000 – 0.014
302 Machine Drawing

 50e8

15

15
15
130

7
8 8H 15
6
28 Pin hole  4, 6 deep
4. Disc
G.M. 1–OFF

30
20

Sung recess
3
8
15

 64
 71
 94
40

R6

R60
 68H7
15

72
18

 50H8
200
Pin hole  4, 6 deep
1. Body 3. Shaft
C.I. 1–OFF M.S. 1–OFF
5
6

 50H7 Pin  4,
 12 long
78

5. Pin
M.S. 1–OFF
12
8

15
40

Sung 3
8 wide
68g6
15

2. Bush
G.M. 1 –OFF

Fig. 17.14. Details of foot step bearing

Solution:
1. The general arrangement of Foot Step Bearing as shown in Figs. 17.15 and 17.16.
Assembly and Details 303

2. The assembly of Foot Step Bearing is as shown in Fig. 17.17. The part list along with fit chart is
also shown.
Shaft

Bush

Disc

Body

Fig. 17.15. General arrangement of foot step bearing

Shaft

Bush

Body

Disc

Fig. 17.16. General arrangement of assembly of foot step bearing

304 Machine Drawing

15
15

8H7/g6
130

28

30
20

4
3
8
8
15

2
 50H8/e8
5  94
40

1  68H7/h6

A
15

A
18

200

Pin hole  4, 6 deep A

Fig. 17.17. Assembly of foot step bearing

Part List
Part No. Part name Material Quantity
1 Body Cast Iron 1
2 Disc Gun Metal 1
3 Bush Gun Metal 1
4 Shaft Mild Steel 1
5 Pin Mild Steel 1
 Assembly and Details 305

Fit Chart

50 H8/e8 Clearance Fit

68 H7/h6 Clearance Fit

8H7/g6 Clearance Fit

17.5.2 Pedestal Bearing (Plummer Block)

Problem 6. The Fig. 17.18 (see figure on next page) shows details of pedestal bearing. Draw the assembly.
Also prepared the bill of material along with fit chart.
Tolerance Chart

48 H7 = + 0.025 48 g6 = – 0.009
+ 0.000 – 0.025

46 H7 = + 0.025 46 g6 = – 0.009
+ 0.000 – 0.025

8 H7 = + 0.015 8 h6 = – 0.009
+ 0.000 – 0.000

56 H7 = + 0.030 56 g6 = – 0.010
+ 0.000 – 0.029

Solution:
1. The general arrangement of Pedestal Bearing as shown in Figs. 17.19 and 17.20.
2. The assembly of Pedestal Bearing is as shown in Fig. 17.21. The part list along with fit chart is also
shown.
306 Machine Drawing

SQ.26

R54

8
48H7

28
R8

20 12 48H7

98
208
CRS78
56H7

28
16

R2
4
 8H7 M12
4

4
68

R8
14

4. Bolt
M.S. 2–OFF
8

10
3

SQ.26 10

CRS162 Spot to suit nut

1. Body
C.I. 1–OFF CRS78
 64
12

16
8

16
M12
24

 48g6
46g6

4
R2
64
28

8
6. Lock nut Oil hole  4 56g6
M.S. 2–OFF

5
 44 R1 R54
46g6
12

R8
X
8

Oil hole  4

M12 3. Cap

 32
C.I. 1–OFF
5. Nut
M.S. 2–OFF
8

8h6

2. Brass
G.M. 1–OFF

Fig. 17.18. Details of pedestal bearing

Assembly and Details 307
Nut Lock nut

Cap

Brass

Body Body
(Bottom view)

Bolt

Fig. 17.19. General arrangement of pedestal bearing

Cap
Nut
Lock nut Brass

Body

Bolt

Fig. 17.20. Assembly arrangement of pedestal bearing

308 Machine Drawing

 64
2 A
B

8
A

R 54
46H7/g6

R8

12
28

64
A
48H7/g6
A
5 20
M12
6 B
6
12

3
8

R48
12

56H7/g6
24

16

32


4
68

1 R8 4
8

 8H7/h6
14

10
7

SQ. 26
3

10 78 CRS

162 CRS B
208

Fig. 17.21. Assembly of pedestal bearing

Part List
Part No. Part name Material Quantity
1 Body Cast Iron 1

2 Brass Gun Metal 1

3 Cap Cast Iron 1
4 Bolt Mild Steel 2
5 Nut Mild Steel 2
6 Lock Nut Mild Steel 2

Fit Chart
8 H7 / h6 Clearance Fit
48 H7/ g6 Clearance Fit
46 H7 / g6 Clearance Fit
56 H7 / g6 Clearance Fit
 Assembly and Details 309

Problem 7. The Fig. 17.22 shows details of pedestal bearing. Draw the assembly. Also prepared the bill
of material along with fit chart.
Tolerance Chart
70 H7 = + 0.030 70 g6 = – 0.010
+ 0.000 – 0.029
58 H7 = + 0.030 58 g6 = – 0.010
+ 0.000 – 0.029
50 H7 = + 0.025
+ 0.000

7
1

58H7
30

18

14

M16  1.5
25 R20
70H7

15
22

R8 5. Hex. nut
76

22 (M.S., 2–OFF)
3

14

16

SQ. 28 14
3

102 CRS
30 200 CRS 30

1. Body
 50H7 C.I., 1–OFF 0
R2
10

58

M16  1.5
58g6

38
76

102 CRS
 12
 6  17
25
10

Oil hole 3
5
16
10
104

11

35
18

R5

28

Sung  6
7

To suit
82

brasses 70g6 Flats



12

 50H7 102 CRS


66

3. Cup
SQ. 26 C.I.,1–OFF
70g6
4. Bolt
2. Brass M.S., 2–OFF
G.M., 1–OFF
Fig. 17.22. Details of pedestal bearing
310 Machine Drawing

Solution:
1. The general arrangement of Pedestal Bearing as shown in Fig. 17.23.
2. The assembly of Pedestal Bearing is as shown in Fig. 17.24. The part list along with fit chart is
also shown.

Nut
Washer

Cap

Brass Cap
Bottom view

Body

Bolt

Body
Bottom view

Fig. 17.23. General arrangement of pedestal bearing

Assembly and Details 311
260
30  82 30
2 A
B

9
R2
58H7/g6

18
25

A
5
M16
B

70H7/g6 3
16

A
22

5 6
0H A
7
A
76

1
R

4
8
3

16
SQ. 28 200 CRS
30 30
102 CRS B

Fig. 17.24. Assembly of pedestal bearing

Part List

Part No. Part name Material Quantity

1 Body Cast Iron 1

2 Brasses Gun Metal 2

3 Cup Cast Iron 1

4 Bolt Mild Steel 2

5 Nut Mild Steel 2

Fit Chart
58 H7 / g6 Clearance Fit
70 H7/ g6 Clearance Fit