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Dimensioning

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Title: Alphabet of Lines Author: 007 - Kirby, John L Last modified by: Cristi Holbrook Created Date: 12/29/2010 2:50:07 PM Document presentation format – PowerPoint PPT presentation

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Title: Dimensioning


1
Dimensioning
  • Standards
  • and
  • Techniques

2
Organizations for Dimension Standards
  • American National Standards Institute a U.S.
    organization that recommends standards for many
    products in various industries. Abbreviation
     ANSI
  • The American Society of Mechanical Engineers
    (ASME) is a professional body, specifically an
    engineering society, focused on mechanical
    engineering.
  • The International Standards Organization - widely
    known as ISO, is an international-standard-setting
    body composed of representatives from various
    national standards organizations.

3
Functions of Dimensioning
  • Conveys communication to the drawing
  • Provides clarity
  • Describes necessary processes
  • Describes the scale, size, and location of
    features on an object
  • Must comply to standards

4
Objectives to Learn
  • Recognition of lines
  • Dimension lines, extension lines, and center
    lines
  • Review alphabet of lines and relationship to
    dimensioning
  • Placement and location of dimensions
  • Ease of reading, legibility, practicality, etc.
  • Choice of dimensions
  • Style - Fractional, decimal, metric, or dual
  • Systems aligned or unidirectional

5
Aligned Dimensioning
  • Aligned Dimensioning most often used in today
    in architectural drawings

Dimensions are rotated on the vertical plane
6
Unidirectional Dimensioning
  • Unidirectional often used in engineering
    drawings

Dimensions are not rotated on the vertical plane.
7
Dimension Line
  • Thin, dark, solid line
  • Terminated with arrowheads
  • Indicate direction and extent of dimension

Dimension Line
8
Extension Line
  • Thin, dark, solid line
  • Extends from object line to ends of dimension
    line
  • Locates position of the dimension
  • Extension lines do not connect to object lines

Extension Line
9
Dimension Text
  • Provides communication with regard to sizes
  • Can also provide communication for location
  • Provides clarity to relationships of features

Dimension Text
10
Arrowheads
  • Used to indicate extent of dimension
  • Should be uniform in size and style
  • There are many styles and types

Arrowhead
11
Arrowhead Styles and Tick Marks
SolidWorks Arrowhead Styles
AutoCAD Arrowhead Styles
12
Dimensioning Symbols
13
Dimension Text
Dimension Line
Extension Line
Dimension Text illustrates the actual size of an
object. Dimension Line with arrow heads are
drawn the length of the dimension. Extension
Lines are drawn from the edges of the object that
represent the dimension.
14
Dimension Location
Dimensions should be located between views
whenever possible.
15
Dimension Placement
Extension lines are located 1/16 off of the
object line and extend 1/8 above the arrowhead.
Shorter dimensions are located inside of longer
dimension and 3/8 away from the object line.
Longer dimensions are located outside of shorter
dimensions and 1/4 away from the dimensions
inside.
16
Dimensioning Angles
Coordinate Method specifies the two location
distances of the angle Angular Method
specifies one location distance and the angle
Angular Method
Coordinate Method
17
Leader Line
Leader Text
Diameter Symbol
Radius Symbol
Leader Line drawn with arrowhead pointing to the
center of the circle. Leader Symbol for diameter
(O with a slash through the center). Leader Text
completes the dimension for the diameter of the
cylinder.
18
Dimensioning Circles and Arcs
Arrow can be inside of small arcs.
Large Arcs use center marks
Small arcs do not need center marks.
19
Dimensioning on Contours
Views are drawn to describe shapes and features.
Dimensions should be given where shapes are drawn.
Incorrect placement of dimensions on the drawing
on the right.
20
Dimensioning Diameters
Diameter annotations are represented on drills or
bores.
Radii annotations for rounds and fillets.
Full circular objects should be dimensioned using
the diameter.
21
Dimensioning Diameters
Diameter dimensions are better represented on
left view of this drawing.
Dimensions are too crowded to be represented on
right side view .
Remember dimension between views whenever
possible.
22
Dimensioning Radial Patterns
Location of holes center to holes are located on
a center line circle and angles based from
center of figure.
23
Dimensioning Curves
Location for curve on the gasket is based on
center marks inside and outside the figure.
24
Dimensioning Curves
Curved or noncircular shapes can be dimensioned
with coordinate dimensions or datums as
illustrated below
Dimensions should be centered between extension
lines except when in a stack. They are then
staggered as represented above
25
Leader Line Locations
Notes with leaders are generally placed off of
the drawing figure as represented here.
Leader lines can cross object lines and extension
lines when necessary as illustrated above.
26
Dimensioning Notes
Notes should always be lettered horizontally on
the sheet and be brief and clear. Wording should
be standard form.
27
Long Break Line
Long Break Lines are used when it is best to
shorten the long view of an object.
28
Dimension Tolerances
  • Allows a range of acceptable variability
  • Assures assemblies will fit properly
  • Parts can be manufactured within a range of
    tolerances rather than exact
  • High precision means high cost

29
Dimensioning with Tolerances
The drawing illustration below represents a
tolerance of 1/32 or .03125 plus or minus range
of accuracy.
30
Dimension Tolerances
Tolerance stacking is avoided by dimensioning
with respect to a datum baseline as illustrated
on the right figure. Errors often occur in
cumulative dimensions.
A cumulative tolerances
B base-line dimensioning
31
Dimensioning Tips to Know
  • Fractional dimensions are generally used on
    cabinet drawings
  • Decimal dimensions are used on engineering
    drawings
  • Feet and inch dimensions are used on
    architectural drawings
  • Tolerances are dimensioned when assembly parts
    are necessary

32
Test your knowledge on the rest of the slides
after reviewing the dimension rules from your
class text.
33
What is wrong with the placement location of
these dimensions?
The longer dimensions have been positioned inside
of the shorter dimensions.
34
What is wrong with the placement location of
these dimensions?
Dimensions should be located outside the object
lines whenever possible to avoid confusion.
35
What is wrong with the dimensions below?
The drawing is over dimensioned. It is not
necessary to include the inside shorter
dimensions.
36
What is wrong with the dimensions below?
The drawing is over dimensioned. Do not repeat
dimensions. They are represented only once.
37
What is wrong with the dimensions below?
The dimensions are difficult to read on the
right view. They should be placed on the left
view.
38
What is wrong with the dimensions below?
The dimensions text should not be on the object
line. Makes the dimension difficult to read.
39
What is wrong with the dimensions below?
The circular dimension should be dimensioned as a
diameter not a radius.
The radial dimension should be dimensioned as a
radius not a diameter.
40
What is wrong with the dimensions below?
The vertical dimension is needed to locate the
beginning of the slant.
41
What is wrong with the dimensions below?
The angular dimension is difficult to read. It
should be positioned off the object line.
42
What is wrong with the dimensions below?
Avoid dimensioning hidden lines and poor
referencing of vertical dimensions.
43
What is wrong with the dimensions below?
A better dimensioning practice.
Dimension between views whenever possible.
44
What is wrong with the dimensions below?
The dimension locations are fine on this
drawing. What can be done to improve it?
This is an engineering drawing. Decimals units
would be better.
45
What is wrong with the dimensions below?
You cannot locate the proper locations for the
proper position of the holes on the radial
dimension without the angular distance.
46
What is wrong with the dimensions below?
The right side view and the isometric view are
not necessary to complete this drawing.
The overall length of 4.75 is also not necessary
to complete this drawing.
47
What is wrong with the dimensions below?
Dimensions should be placed on the contour view
for clarity.
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