Mechanical drafting introduction to graphical language, its importance and its need, types of machine drawing, types of lines, design of fasteners, types of fasteners, screwed fasteners, types of bolts, types of nuts, types of screws, types of rivets, types of keys, lock nuts and foundation bolts

1. Mechanical Drafting
Introduction to MechanicalDrafting
and Fasteners
Gaurav Mistry
AssistantProfessor
Diwaliba Polytechnic, UTU.

2. Gaurav Mistry 2
 Overview of MD MechanicalDrafting

3. Gaurav Mistry 3
 Introduction to MD MechanicalDrafting
Importance of Graphic Language
 Engineering drawing is a suitable graphic language from which any
trained/technical person can visualize the required object. As an engineering
drawing displays the exact picture of an object, it obviously conveys the same
ideas to every trained eye.
 Irrespective of language barriers, the drawings can be effectively used in other
countries, in addition to the country where they are prepared. Thus, the
engineering drawing is the universal language of all engineers.
 In the absence of graphic language, the ideas on technical matters have to be
conveyed by speech or writing, both are unreliable and difficult to understand by
the shop floor people for manufacturing. This method involves not only lot of time
and labour, but also manufacturingerrors.
 Without engineering drawing, it would have been impossible to produce objects
such as aircrafts, automobiles, locomotives, etc., each requiring thousands of
different components.

4. Gaurav Mistry 4
 Introduction to MD MechanicalDrafting
Need of Graphic Language
 The drawings prepared by any technical person must be clear, unmistakable in
meaning and there should not be any scope for more than one interpretation, or
else disputemay arise.
 It would not have been possible to produce the machines/automobiles on a mass
scale without clear, correct and accurate drawings.
 To achieve this, the technical person must gain a thorough knowledge of both the
principles and conventional practice of draughting. If these are not achieved and
or practiced, the drawings prepared by one may convey different meaning to
others, causing unnecessary delays and expenses in productionshops.
 The study of machine drawing mainly involves learning to sketch machine parts
and to make working and assembly drawings. This involves a study of those
conventionsin drawings that are widely adoptedin engineering practice.

5. Gaurav Mistry 5
 Introduction to MD MechanicalDrafting
 Classification of Drawing
 Machine Drawing
 ProductionDrawing
 Part/ Detail Drawing
 Assembly Drawing
• DesignAssemblyDrawing
• InstallationAssemblyDrawing
• Assembly Drawingfor Catalogues
• Assembly Drawingfor InstructionManuals
• Exploded AssemblyDrawing
• SchematicAssemblyDrawing/ BlockDiagram
• MachineShop Drawing
• Patent Drawing

6. Gaurav Mistry 6
 Introduction to MD MechanicalDrafting
 Classification of Drawing

7. Gaurav Mistry 7
 Introduction to MD MechanicalDrafting
 Types of Lines.
Can be considered as Alphabets of Drawing like (A to Z in English)

8. Gaurav Mistry 8
 Fasteners MechanicalDrafting
 Fasteners
 The fasteners are of two types: Permanent and Removable (Temporary).
1. Riveting and welding processes are used for fastening permanently.
2. Screwed fasteners such as bolts, studs and nuts in combination, machine screws,
set screws, etc., and keys, cotters, couplings, etc.
 Screwed Fasteners:
• Screwed fasteners occupy the most prominent place among the removable
fasteners. In general, screwed fasteners are used : (i) to hold parts together, (ii) to
adjust parts with reference to each otherand (iii) to transmit power.
• A screw thread is obtained by cutting a continuous helical groove on a cylindrical
surface (external thread).
• The threaded portion engages with a corresponding threaded hole (internal
thread); forming a screwed fastener.

9. Gaurav Mistry 9
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Followingare the terms that are associated with screw threads.

10. Gaurav Mistry 10
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Design of Screw thread.

11. Gaurav Mistry 11
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Forms Screw thread.

12. Gaurav Mistry 12
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Thread Designation

13. Gaurav Mistry 13
 Fasteners MechanicalDrafting
 Screwed Fasteners:

14. Gaurav Mistry 14
 Fasteners MechanicalDrafting
 Screwed Fasteners:
ConventionalRepresentation
of Threads
 The crests of threads are indicated
by a continuous thick line and the
roots, by a continuousthin line.
 For hidden screw threads, the
crests and roots are indicated by
dottedlines.
 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.

15. Gaurav Mistry 15
 Fasteners MechanicalDrafting
 Screwed Fasteners:
ConventionalRepresentation of V threads and Square threads
V threads Square threads

16. Gaurav Mistry 16
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Method of drawing Hexagonal and SquareBolt head (Nut)
Empirical relations (Hexagonal):
• Major or nominal diameter of bolt = D
• Thickness of nut, T = D
• Width of the nut across corners = 2 D
• Radius of chamfer arc, R = 1.5 D
Empirical relations (Square) :
• Major or nominal diameter of bolt = D
• Thickness of nut, T = D
• Width of the nut across corners = 1.5 D + 3 mm
• Radius of chamfer arc, R = 2 D

17. Gaurav Mistry 17
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Types of Bolts

18. Gaurav Mistry 18
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Types of Nuts
Hexagonal Nut
Square Nut

19. Gaurav Mistry 19
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Types of Machine Screws and Set Screws.

20. Gaurav Mistry 20
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Locking Arrangement for Nuts

21. Gaurav Mistry 21
 Fasteners MechanicalDrafting

22. Gaurav Mistry 22
 Fasteners MechanicalDrafting
 Screwed Fasteners:
Locking Arrangement for Nuts

23. Gaurav Mistry 23
 Fasteners MechanicalDrafting
 Screwed Fasteners:
FoundationBolts

24. Gaurav Mistry 24
 Fasteners MechanicalDrafting
 RemovableFasteners:
Keys
Keys are machine elements used to
prevent relative rotational
movement between a shaft and the
parts mounted on it, such as
pulleys, gears, wheels, couplings,
etc.

25. Gaurav Mistry 25
 Fasteners MechanicalDrafting
 PermanentFasteners:
Rivets
Riveted joints are permanent
fastenings and riveting is one of
the commonly used method of
producing rigid and permanent
joints. Manufacture of boilers,
storage tanks, etc., involve joining
of steel sheets, by means of riveted
joints.

26. Gaurav Mistry 26
REFERENCES:
1. Machine Drawing, K. L. Narayan, New Age Int. Pub.
2. Mechanical Drafting, S. V. Gosai, Atul prakashan.
3. www.google.com
MechanicalDrafting