This document discusses different dimensioning systems used in engineering drawings including aligned, unidirectional, chain, parallel, and combined systems. It describes the key aspects of each system such as placement of dimensions, leaders, arrowheads, and extension lines. Dimensioning techniques for various geometric features like holes, arcs, and circles are also covered along with examples of front and side views showing the aligned and unidirectional systems.

1. Shree S’ad Vidya Mandal
Institute Of Technology
ENGINEERING GRAPHICS
Branch: - Mechanical – 02
Group :- 01
Guided Name:-
 Topic : - All Dimensioning system.
Prepared By : -
1. DHAVAL S. PATEL. 63
2. DHRUMIL J. PATEL . 64
3. HARSH J. PATEL. 65
4. JAY J. PATEL. 66

2. Aligned System
In the aligned system, dimensions are aligned with the entity being
measured. They are placed perpendicular to the dimension line
such that they may be read from the bottom or right-hand side of the
drawing sheet. Dimensions are placed at the middle and on top of the
dimension lines.
Unidirectional System
In the unidirectional system, dimensions are placed in such a way that
they can be read from the bottom edge of the drawing sheet.
Dimensions are inserted by breaking the dimension lines at the
middle.
Systems of Dimensioning

3. Dimensioning systems
Aligned system
(readable from bottom and
right edge of sheet)
Unidirectional system
(visible from bottom edge)

4. Dimensioning
Providing information on a drawing about
 Distances (size or functional dimensions)
 Sizes and positions (location or datum dimensions) of
holes, grooves and other features.
 Details relating to manufacture etc.
15
15
30
Roughness 0.5
Location
Location
Size,
functional
Manufacturing detail
Hole f15 Size specification, f – symbol
for diameter

5. Different lines in dimensioning
• Outline - Forms the shape of the object in a view
(drawn dark and continuous)
• Extension line – An extension of an outline or centerline
(drawn light and continuous, used to indicate the
entity being dimensioned)
• Dimension line – Thin continuous line terminated by
arrowheads touching the outlines, extension lines or
center lines (used to specify end points of a
dimension)
Outline
Extension
line50Dimension line Dimension

6. Leader lines and notes
Hole f15 Note
 Leader (or pointer) line – Thin continuous line connecting a note or
dimension figure with the feature to which it applies. One end of the leader
terminates in an arrowhead or dot.
 The arrowhead touches the outline while the dot is placed within the
object or on the outline
 The other end of a leader is terminated in a horizontal line underlining
the note
Leader line
Material: mild steel
Roughness 0.5
Leader line

7. Arrowheads and dimension line positioning
• A dimension line is placed at least 6-8 mm away from an outline and
from each other
• An extension line extends ~3mm beyond a dimension line
• Arrowhead – Placed at each end of a dimension line, its pointed end
touches an outline, extension line or a centerline. It is also placed at
the end of a leader line
~3mm 50
Arrowhead
45o
Open Closed
Closed and
filled Oblique stroke
w
3w
Size of the arrowhead should be
proportional to the length of the
dimension line
~6-8mm

8. Chain (continuous) dimensioning
All the dimensions are aligned in such a way that an arrowhead of one
dimension touches tip-to-tip the arrowhead of the adjacent dimension. The
overall dimension is placed outside the other smaller dimensions

9. Parallel (progressive) dimensioning
All the dimensions are shown from a common reference line.
Obviously, all these dimensions share a common extension line. This
method is adopted when dimensions have to be established from a
particular datum surface
Smaller dimensions should always be placed nearer the view. The
next smaller dimension should be placed next and so on.

10. Combined dimensioning
When both the methods, i.e., chain dimensioning and parallel
dimensioning are used on the same drawing, the method of
dimensioning is called combined dimensioning
15

11. Circular holes
A hole is usually dimensioned by giving its diameter instead of radius. The
dimension indicating a diameter should always be preceded by the symbol ø
They should be dimensioned in the view in which they appear as circles
f40

12. Placing of dimension
Within extension
lines
Outside extension
lines
With leader
7o

13. An arc is usually dimensioned by giving its radius. The
dimension indicating radius should be preceded by symbol
R
The R can be placed after the dimension also
The position of center of arc is denoted by a
Dimensioning arcs

14. O
PICTORIAL PRESENTATION IS GIVEN
THE ALIGNED SYSTEM
ORTHOGRAPHIC PROJECTIONS
X Y
40 20
SQ30
2050
60
30
10
F.V. S.V.
FRONT VIEW L.H.SIDE VIEW
75

15. O
PICTORIAL PRESENTATION IS GIVE
THE UNIDIRECTIONAL
METHOD
ORTHOGRAPHIC PROJECTIONS
FOR T.V.
X Y
FV
O
40
10
10
TV
25
25
30 R
100
1010
f 20
f30