The document discusses various machine drawing conventions including scale, which is the ratio of dimensions on a drawing to the actual object; sectioning, where cutting planes are used to show internal details and designated with capital letters; and different line types used for graphical representation in technical drawings. Specific machine elements like ribs and shafts are not cut or hatched in longitudinal sections.

1. Machine Drawing
- Bearing:- Plummer Block -
S.Gunabalan
Associate Professor
Mechanical Department
Bharathiyar College of Engineering & Technology
Karaikal - 609 609.
Ph: 04368-265915/265916
Fax : 04368-266016
Mobile : 9788223359

2. Symbol of first & Third angle Projections

3. Symbol of first & Third angle Projections
Paper Plane

4. Symbol of first & Third angle Projections

5. Scale
Scale is the ratio of the linear dimension of an
element of an object as represented in the
drawing, to the real linear dimension of the same
element of the object itself.
Designation
SCALE 1 : 1 for full size,
SCALE × : 1 for enlarged scales,
SCALE 1 : × for reduced scales.
The designation of the scale used on the drawing
should be shown in the title block.

6. Lines
• Lines of different types and thicknesses are
used for graphical representation of objects

10. Conventions for Sectioning
1. The objective of sectioning is to show the inner
details of a machine component.
2. A cutting plane cuts the object and the section
is viewed after the removal of cut portion.
3. Cutting planes are designated by capital letters
and the direction of viewing is indicated by
arrow marks.
4. The cutting plane(s) should be indicated by
means of type H line

12. Conventions for Sectioning
1. In principle, ribs, fasteners, shafts, spokes of
wheels and the like are not cut in
longitudinal sections and therefore should
not be hatched.

13. Sections not to be Hatched

14. Sections not to be Hatched

15. Sectioning with two parallel planes

16. Sectioning in two Intersecting Planes

19. Half - Section
Symmetrical parts may be drawn, half in plain
view and half in section.

20. A local section may be drawn if half or full section is
not convenient. The local break may be shown by a
continuous thin free hand line.

21. Successive sections may be placed separately, with
designations for both cutting planes and sections

30. Part - A
Answer All the Questions
1. Draw the symbol of first angle projections?
2. Define scaling in machine drawing ?
3. List the types of line ?
4. How to designated cutting plane ?
5. List few machine element which should not
be hatched ?

31. Part - B
1. Assemble all parts of thePB, shown in Fig. below and draw the following views:
(i) Half sectional view from the front, and
(ii) Top View (iii) Side View
Also make the parts list and bill of materials. Dimension the view completely.