PART 2: DIMENSIONING
Mr. Joseph Aveyire
Department of Agricultural
Engineering
COLLEGE OF ENGINEERING
KNUST-Kumasi
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DIMENSIONING
Learning Objectives
 Be able to explain the importance of dimensioning,
 Be able to apply notations of dimensioning,
 Be able to describe the theory of dimensioning,
 Be able to demonstrate size dimensioning,
 Be able to demonstrate location dimensioning,
 Be able to apply dimensioning.
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DIMENSIONING
Dimensioning:
 Dimensioning is art assigning dimensions, notes, and
conventions to a drawing in order. of an engineering
drawing involve.
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DIMENSIONING
Importance of Dimensioning:
 Provides a clear (avoids inherit errors in drawing
and reading of objects) and complete description of
an object,
 The dimensioning of machine elements facilitates
the end-use of the drawing
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DIMENSIONING
End –Use of Dimensioning:
 Functional oriented,
 Manufacturing oriented,
 Control (inspection) oriented.
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DIMENSIONING
Notations of Dimensioning
a. Dimension Line:
Dimension line is a thin continuous line used:
 to indicate the measurement,
 to indicate the direction of measurement,
 The first dimension line is about 10mm from the
object line,
 Subsequent dimension lines are about 7mm from
previous dimension line.
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DIMENSIONING
Notations of Dimensioning
a. Dimension Line:
 Small features:
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If the dimension cannot be written within the
extension lines:
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DIMENSIONING
Notations of Dimensioning
a. Dimension Line:
End of Dimension Line:
This can be:
 an arrow
 Dot
 or slash (backward or forward)
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DIMENSIONING
Notations of Dimensioning
b. Extension (Projection) Line:
It is a thin continuous line that begins with:
 An offset of about 1 mm from the object line,
 An extension of about 3mm beyond the dimension
line.
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DIMENSIONING
Notations of Dimensioning
b. Note:
Notes on a drawing give complete information
regarding specific operation relating to the feature.
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DIMENSIONING
Notations of Dimensioning
e. Symbols:
A symbol is a presentation of an object by some mark
on the drawing.
Symbol
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DIMENSIONING
Notations of Dimensioning
e. Leader:
• It is a thin continuous line drawn from the note to
the feature in the view where it applies.
Leader
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DIMENSIONING
Notations of Dimensioning
f. Dimensions:
• Engineering units of dimension are millimetres and
therefore not specified,
• Units other than mm should be specified eg. 1/2", 45°
etc.,
• Dimensions should best be placed outside the view,
• Dimensions should not be placed within hatched
areas,
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DIMENSIONING
Notations of Dimensioning
f. Dimensions:
• But should that be unavoidable then the portion of
the area around the figure should be unsectioned.
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DIMENSIONING
Notations of Dimensioning
f. Dimensions:
• Underlined: object is dimensioned not to scale
• Elliptical Framed: Implies the dimension is for
80
checking
• Square Framed: Implies theoretical dimension
• Partition Framed:
% specification for checking
parts
• Bracketed: For auxiliary dimension
(80)
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DIMENSIONING
Notations of Dimensioning
f.
Dimensions:
Systems of Placing Dimensions
•
Aligned system:
line.
Dimensions are aligned to dimension
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DIMENSIONING
Notations of Dimensioning
f.
Dimensions:
Systems of Placing Dimensions
•
•
Aligned system:
Unidirectional system: Dimensions are placed so that
they can be read from the bottom or right edge of the
drawing sheet
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DIMENSIONING
Theory of Dimensioning
The dimensioning of a drawing can be achieved by the
following steps:
1. Size and location dimensioning,
2. Dimensioning to Suite Purpose of the Drawing,
3. Elimination of redundant dimensions,
4. Style of dimensioning.
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DIMENSIONING
Theory of Dimensioning
1. Size and location dimensioning,
An object can be considered to be made up:
 Simple geometrical shapes (prism, cylinder,
pyramid, cone, sphere etc.),
 These geometric shapes may be either solid or
hollow,
 These geometric shapes may be identified by size
parameters.
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DIMENSIONING
Theory of Dimensioning
1. Size and location dimensioning,
Size Dimensions (individual and entire geometry):
 Include dimensions such a length, width, height,
diameter, enclosed angle etc.,
 Geometric objects can be identified by their size
dimensions, e.g. cylinder by its diameter and
height,
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DIMENSIONING
Theory of Dimensioning
1. Size and location dimensioning,
Location Dimensions:
 Locate the position of-an object by its feature (e.g.
surface, edge, etc.) with respect to a reference feature,
 Coordinate systems are used in expressing location
dimension,
 Cartesian coordinate system,
 Polar coordinate system.
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DIMENSIONING
Theory of Dimensioning
1. Size and location dimensioning,
Location Dimensions: Setting the origin.
 Identify a reference geometric object,
 Identify reference features on this reference object to
act as reference axis, and therefore
 Identify the origin.
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DIMENSIONING
Theory of Dimensioning
1. Size and location dimensioning,
Location Dimensions: By Cartesian Coordinate System
Axes could be represented by:
a. Edges of surfaces
b. Symmetrical axes
c. Centres of holes
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DIMENSIONING
Theory of Dimensioning
1. Size and location dimensioning,
Location Dimensions: By Cartesian Coordinate System
Axes could be represented by:
a. Edges of surfaces
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DIMENSIONING
Theory of Dimensioning
1. Size and location dimensioning,
Location Dimensions: By Cartesian Coordinate System
Axes could be represented by:
b. Symmetrical axes
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DIMENSIONING
Theory of Dimensioning
1. Size and location dimensioning,
Location Dimensions: By Cartesian Coordinate System
Axes could be represented by:
c. Centre of holes
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DIMENSIONING
1. Size and location dimensioning,
Location Dimensions:
 Modes of specifying Cartesian coordinates:
A. Absolute Cartesian coordinates:
they are coordinates entered with respect to
reference features of the reference object,
B. Relative Cartesian coordinates:
they are coordinates entered with respect to
features of a located object.
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DIMENSIONING
Theory of Dimensioning
2. Dimensioning to Suite Purpose of the Drawing,
 Refine size and location dimensions to suit the
purpose of the drawing
 End use of a drawing may be:
a. Functional,
b. Manufacturing and
c. Control
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DIMENSIONING
Theory of Dimensioning
2.
Dimensioning to Suite Purpose of the Drawing,
a. Functional and Non-functional Dimensions
b. Functional dimensions can be size or location
dimensions of functional features.
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DIMENSIONING
Theory of Dimensioning
2. Dimensioning to Suite Purpose of the Drawing,
b. Manufacturing
 The dimension can be used directly during the
production without modification.
 There are various manufacturing processes
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DIMENSIONING
Theory of Dimensioning
2. Dimensioning to Suite Purpose of the Drawing,
b. Manufacturing
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DIMENSIONING
Theory of Dimensioning
2. Dimensioning to Suite Purpose of the Drawing,
c. Control
These dimensions are required to control the quality of
the products.
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DIMENSIONING
Theory of Dimensioning
3. Auxiliary / Redundant dimensions,
 Auxiliary dimensions are additional information,
 They are not used for functional purposes, but could
be used in manufacturing. E.g overall size dimension.
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DIMENSIONING
Theory of Dimensioning
4. Style of dimensioning.
i. Chain dimensioning
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DIMENSIONING
Theory of Dimensioning
4. Style of dimensioning.
ii. Parallel dimensioning
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DIMENSIONING
Theory of Dimensioning
4. Style of dimensioning.
iii. Combined dimensioning
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DIMENSIONING
Theory of Dimensioning
4. Style of dimensioning.
iv. Progressive dimensioning
Point of origin:
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General Rules for Dimensioning
All dimensions necessary for the description of the
part should be provided,
ii. Dimensions should be given on the view that shows
the relevant feature clearly,
iii. Dimensions marked in one view must not be
repeated in other views,
i.
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General Rules for Dimensioning
iv. Dimensions should be placed outside the view,
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General Rules for Dimensioning
v. Dimensions should be taken from visible outlines
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General Rules for Dimensioning
vi. Dimensions should be given from a base line or
centre line of a hole or a finished surface
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General Rules for Dimensioning
vii. Crossing of dimension lines by either an extension
or another dimensional line should be avoided
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General Rules for Dimensioning
vii. Crossing of dimension lines by either an extension
or another dimensional line should be avoided
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CHECK ERRORS
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DIMENSIONING
Exercise 1: Identify simple geometric objects
1: Solid cylinder
2: Hollow cylinder
3: Solid rectangular prism
4: Solid half disc
5: Hollow cylinder
6: Solid rectangular prism
7: Solid rectangular prism
8: Hollow cylinder
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DIMENSIONING
Size dimensioning of simple geometric objects
S1
S5
S4
S3
S6
S7
S2
S8
S7
S6
S4
S5
S1
S3
S2
S3
S8
S7 S6
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DIMENSIONING
Location Dimensioning:
 Only positive values are considered
Y
Z
X
z
x
y
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DIMENSIONING
Location dimensioning of simple geometric objects
Y
L6Y L5Y
L4Y
L8y
L8x
X
x
L3Y
L3X
L4X
y
L5X
L6X
Z
z
L7z
L5Z
X
L4Z
L8z
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DIMENSIONING
End-use dimensioning = Functional (size)
F5s
F2s
F8s
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DIMENSIONING
End-use dimensioning = Functional (location)
Y
L5Y
L8y
L8x
X
x
y
L5X
L6X
Z
z
L7z
X
L5Z
L8z
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