14834 dimension ing principles
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PRINCIPLES
OF DIMENSIONING
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ShapeMultiviewDrawing
Dimensioning
Designa part
1. Size, Location
ENGINEERING DESIGN
2. Non-graphic information
TRANSFERREDINFORMATION
Createdrawings
Manufacture
RESULT
Sketchesof ideas
PROCESS
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To describe an object
completely
we need to define both
the shape
and the size.of the object
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DEFINITION
Dimensioning is the process of specifying part’ s
information by using of figures, symbols and notes.
This information are such as:
1. Sizes and locations of features2. Material’s type
3. Number required
4. Kind of surface finish5. Manufacturing process
6. Size and geometric tolerances
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ELEMENTS OF DIMENSIONING
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L
L
S
S
S
Designed part
S
L
L
INFORMATION CONVEYED:
Dimension
But how?
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ELEMENTS OF DIMENSIONING
EXTENSION LINE
ARROW HEADS
DIMENSION LINE
DIMENSION
LEADER LINE
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indicate the location on the object’s features
that are dimensioned.
EXTENSION LINES
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EXTENSION LINES
Leave a visible gap (≈ 1 mm) from a view and start
drawing an extension line.
Extend the lines beyond the (last) dimension line
1-2 mm.
Visible gap
COMMON MISTAKE
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Do not break the lines as they cross object lines.
COMMON MISTAKE
Continuous
EXTENSION LINES
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Arrowheads
Types of arrow heads and their Order of Preference(Left to Right)
1st 2nd 3rd 4th
w
3w
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DIMENSION LINES
indicate the direction and extent of a dimension, andinscribe dimension figures .
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1 3
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indicate details of the feature with a
local note.
LEADER LINES
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1 3
10 Drill, 2 Holes
R16
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Dimension lines should not be spaced too close
to each other and to the view.
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1
3
4
Leave a space at least2 times of a letter height.
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3
5
DIMENSION LINES
Leave a space at least
1 time of a letter height. 14
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DIMENSION FIGURESThe height of figures is suggested to be 2.5~3 mm.
Place the numbers at about 1 mm above dimension
line and between extension lines .
COMMON MISTAKE
1 1
1 1
3 4
3 4
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16.2516.25
or
DIMENSION FIGURES
When there is not enough space for figure orarrows, put it outside either of the extension lines.
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Not enough spacefor figures
Not enough spacefor arrows
1 1
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The JIS and ISO standards adopt the unit of
Angular dimension in degree with a symbol “o”
place behind the figures (and if necessary
minutes and seconds may be used together).
DIMENSION FIGURES : UNITS
Length dimension in millimeters without
specifying a unit symbol “mm”.
JAPANESE INDUSTRIAL STANDARDSINTERNATIONAL ORGANIZATION FOR STANDARDS
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1. Aligned method
2. Unidirectional method
The dimension figures are placed so that they are readable from the
bottom and right side of the drawing.
The dimension figures are placed so that they can be read from the
bottom of the drawing.
Do not use both system on the same drawing or on the same series ofdrawing (JIS Z8317)
DIMENSION FIGURES : ORIENTATION
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3 0
30
30
3 0
EXAMPLE : Dimension of length using aligned method.
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30
30
30
30
3030
30
30
EXAMPLE : Dimension of length using unidirectional method.
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45o
4 5 o
45o
4 5 o
EXAMPLE : Dimension of angle using aligned method.
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45o
45o
45o
45o
45o45o
45o
45o
EXAMPLE : Dimension of angle using unidirectional method.
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Fundamental Principles of
Dimensioning
•Clarity
•Essentiality
•Functionality
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THE BASIC CONCEPT
Dimensioning is accomplished by adding size and locationinformation necessary to manufacture the object.
Clear
Complete
Facilitate the- manufacturing method- measurement method
This information have to be
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L
L
S
S
S
Designed
part
EXAMPLE
To manufacture this partwe need to know…
1. Width, depth and
thickness of the part.
2. Diameter and depthof the hole.
3. Location of the holes.“S” denotes size dimension.
“L” denotes location dimension.
S
L
L
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ANGLETo dimension an angle use circular dimension line having the centre
at the vertex of the angle.
COMMON MISTAKE
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ARCArcs are dimensioned by giving the radius, in the
views in which their true shapes appear.
The letter “R” is always lettered before the figures
to emphasize that this dimension is radius of an
arc.
or
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ARCThe dimension figure and the arrowhead should be inside the arc,
where there is sufficient space.
R 62.5
Move figure outside
R 6.5
Move both figure
and arrow outside
Sufficient space
for both.
Sufficient space
for arrowhead only.
R 58.5
Insufficient space
for both.
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ARCLeader line must be radial and inclined withan angle between 30 ~ 60 degs to the horizontal.
COMMON MISTAKE
R62.5
R62.5
R62.5
R62.5R62.5
R62.5
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ARCUse the foreshortened radial dimension line,
when arc’ s center locates outside the sheet or
interfere with other views.
Drawing sheet
Method 1Method 2
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FILLETS AND ROUNDSGive the radius of a typical fillet only by using a local note.
R6.5
If all fillets and rounds are uniform in size, dimension may be omitted,
but it is necessary to add the note “ All fillets and round are Rxx. ”
NOTE:All fillets and round are R6.5
Drawing sheet
R12
unless otherwise specified.NOTE:All fillets and round are R6.5
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The curve constructed from two or more arcs, requires the dimensions of radii
and center’s location.
CURVE
COMMON MISTAKE
Tangent point
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CYLINDERSize dimensions are diameter and length.
Measurementmethod
Location dimension must be located from its center lines and should be givenin circular view.
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1 0 0
7 0
CYLINDER
Diameter should be given in a longitudinal view with the symbol “ ” placed
before the figures.
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HOLESSize dimensions are diameter and depth.
Location dimension must be located from its
center lines and should be given in circular view.
Measurementmethod
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xx
Use leader line and local note to specify diameter
and hole’s depth in the circular view.
HOLES : SMALL SIZE
xx Drill, Thru.
1) Through thickness hole
xx Thru.
or
xx Drill.
or or
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xx, yy Deep
HOLES : SMALL SIZE
or
xx Drill, yy Deep
Hole’s
depth
Use leader line and local note to specify diameter
and hole’s depth in the circular view.
2) Blind hole
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xx
Use extension anddimension lines
Use diametraldimension line
Use leader lineand note
HOLES : LARGE SIZE
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COMMON MISTAKE
xx xx xx
Rxx
xx
HOLES
xx
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CHAMFERUse leader line and note to indicate linear
distance and angle of the chamfer.
SS q
For a 45o chamfer
S SCS
or
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ROUNDED-END SHAPES
R12 12
21
5
Dimensioned according to the manufacturing method used.
Center to Center Distance
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ROUNDED-END SHAPES
R12
21
5
1 2
Dimensioned according to the manufacturing method used.
Center to Center Distance
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ROUNDED-END SHAPES
Dimensioned according to the manufacturing method used.
R12
21
1 2
16
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ROUNDED-END SHAPES
R12
27
1 2
Dimensioned according to the manufacturing method used.
Tool cutting distance
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ROUNDED-END SHAPESDimensioned according to the standard sizes of another part to be assembled
or manufacturing method used.
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Key
(standard part)
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ROUNDED-END SHAPESDimensioned according to the standard sizes of another part to be assembled
or manufacturing method used.
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CHAIN PARRALEL
DIMENSIONING METHODS
CHAIN DIMENSIONING
PARALLE DIMENSIONING
COMBINED DIMENSIONING
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Redraw and Correct thedimensions shown in thediagram on the left handside using proper standardand dimensioning rules.
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Redraw and Correct thedimensions shown in thediagram on the left handside using proper standardand dimensioning rules.
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RULES OF DIMENSIONING : A summary
Between any two extension lines, there must be one and only one dimension line
bearing one dimension.
As far as possible, all the dimensions should be placed outside the views. Inside
dimensions are preferred only if they are clearer and more easily readable.
All the dimensions on a drawing must be shown using either Aligned System or
Unidirectional System. In no case should, the two systems be mixed on the same
drawing.
The same unit of length should be used for all the dimensions on a drawing. The unit
should not be written after each dimension, but a note mentioning the unit should be
placed below the drawing.
Dimension lines should not cross each other. Dimension lines should also not cross any
other lines of the object.
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RULES OF DIMENSIONING : A summary
All dimensions must be given.
Each dimension should be given only once. No dimension should be redundant.
Do not use an outline or a centre line as a dimension line. A centre line may be
extended to serve as an extension line.
Avoid dimensioning hidden lines.
Smaller dimensions should always be placed nearer the view. The next smaller
dimension should be placed next and so on.
All notes should be written horizontally.
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SYSTEMS OF DIMENSIONING: A SUMMARY
Aligned System
In the aligned system, dimensions are placed perpendicular to the dimension
line so 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. As shown in Fig. 3.5, all
horizontal dimensions are placed at the middle and on top of the dimension
lines while vertical and inclined dimensions are inserted by breaking the
dimension lines at the middle.