Sectional Views

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Sectional Views
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Terms

• Conventional break
• Shortened view of a long simple object
• Cutting plane
• An imaginary plane used to cut through an object
• Sectional view
• View that shows an internal portion of an object
• Part of the object cut away

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Terms

• Sectional view
• A line symbol that is drawn on an exposed, cut
  surface
• Section symbols
• Symbolic section lining used for indication of
  various materials
• Subtitles
• Labeling with capital letters the sectional view
  which has a removed section
• Symmetry
• Being the same on opposite sides of a center line

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Types of Sectional Views
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Full Section

• Overhead

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Half Section

• Overhead

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Offset Section

• Overhead

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Broken-Out Section

• Overhead

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Revolved Section

• Overhead

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Removed Section

• Overhead

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Aligned Section

• Overhead

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Rib Section

• Overhead

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Assembly Section

• Overhead

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Section Details
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Full Section

• Replaces an exterior view in order to show some
  interior details

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Half Section

• Used to show both interior exterior features of
  a symmetrical object

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Offset Section

• Used to show features that are not in a straight
  line

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Broken-out Section

• Used to show interior detail of objects where
  less than half section is required

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Revolved Section

• Used to show the true shape of the cross section
  of a long object such as a bar, spoke, rib, or arm

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Removed Section

• Used for clearness for easier dimensioning
• Similar to revolved section except it is placed
  off the part

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Aligned Section

• Used when true projection would be confusing for
  spokes, ribs, holes

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Rib Section

• Method of not showing the ribs section lined to
  eliminate the impression of solidity

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Assembly Section

• Shows all parts of an object as one unit
• Drawn using section lining
• Makes the individual parts stand out

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General Rules in Sectioning

• Should be projected in the normal orthographic
  view
• Exception
• Revolved sections removed sections

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General Rules in Sectioning

• Two or more sections appear on the same drawing
• Cutting plane lines are labeled the view is
  subtitled

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General Rules in Sectioning

• Arrowheads
• Indicate the direction in which the section is
  viewed
• Sectional views are not made from another
  sectional view, except for clarity

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General Rules in Sectioning

• Sections should be drawn at the same scale as the
  views from which they were taken
• Sections should appear on the same sheet as the
  drawing from which they were taken
• If placed on a separate sheet
• The section view should be oriented as it was
  projected from the cutting plane cross
  referenced by zone designations

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General Rules in Sectioning

• Section lines are thin parallel lines
• Drawn at angle to main outline
• Usually 45ø

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General Rules in Sectioning

• Section lines are uniformly spaced
• Spacing should increase as the size of the
  drawing increases
• Minimum space of .18 is used for microfilm
• Large surfaces
• Often sectioned only along the edge of part

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General Rules in Sectioning

• Assembly sectionals
• Section lines of adjacent parts drawn at a 30ø,
  45ø, or 60ø angles

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General Rules in Sectioning

• Visible lines behind the cutting plane
• Shown
• Hidden lines behind the cutting plane
• Omitted

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General Rules in Sectioning

• One major center line
• Cutting plane line may be omitted
• Only a single section of symmetrical part is
  needed
• Cutting plane line may be omitted

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General Rules in Sectioning

• Cutting plane offsets
• Line is not shown in the sectioned view to
  represent the offset
• When dimensions on sectioned areas are
  unavoidable
• Section lining should be omitted for the numerals
  or lettering

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General Rules in Sectioning

• Half sections
• Hidden lines may be added to the unsectioned half
  if needed for dimensioning
• Center line or a visible line may be used to
  divide the sectioned half from the unsectioned
  half

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Specific Rules

• Full section
• Cutting plane lines section titles generally
  are used but may be omitted if they are obvious
• Half section
• Cutting plane lines section titles are omitted
• Offset section
• Cutting plane lines section titles are required

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Specific Rules

• Broken-out section
• Break line convention is used to separate the
  sectional view portion from the exterior view
• Revolved section
• Cutting plane lines are omitted in symmetrical
  sections
• Removed section
• Often drawn to larger scale cutting plane lines
  are omitted if section is placed right off the
  part

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Types of Conventional Breaks

• Round solid
• Rod
• Some companies do not use the crosshatching on
  these breaks

• Round tubular
• Pipe

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Types of Conventional Breaks

• Round tubular
• Section view

• Rectangular bar
• Metal
• Short break symbol

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Types of Conventional Breaks

• Rectangular bar
• Metal
• Long break symbol

• Rectangular bar
• Wood

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Labeling Sectional Views

• More than one removed section view should be
  labeled with letters corresponding to the ends of
  the cutting plane line
• Sectional views
• Arranged in alphabetical order from left to right
  on the drawing
• Section letters
• Used in alphabetical order
• Letters "I", "O", "Q" should not be used

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Labeling Sectional Views

• Word "section" should not be abbreviated
• Section letters are always used in pairs
• Examples A-A, B-B, C-C, etc
• Drawing uses all the available letters of
  alphabet, additional sections should be indicated
  by double letters in alphabetical order

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Labeling Sectional Views

• Section letters are placed near the arrowheads of
  the cutting plane line

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Line Thickness
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Forms of Cutting Plane Lines
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Section Lining Symbols for Materials
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Common Errors

• Irregular spacing
• Irregular line weights
• Lines too thick
• Lines are short or overrun visible lines

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Use of Unlined Sections

• Thin parts are made solid

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Use of Unlined Sections

• Shafts, bolts, nuts, pins, keys, rivets, gear
  teeth, similar parts
• Should not be sectioned if axis lies in cutting
  plane
• Broken-out section of shaft may be made to
  indicate clearness of key, keyseat, pin

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Equal Spacing of Section Lining

• Visual spacing
• Line guide
• Scribed line on triangle may be used
• Trace lines from a grid sheet
• Measure with scale

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