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A method of representing a three dimensional object
Orthographic Projection
Front view is also referred to as the
key view
Glass Box theory demonstrates what view
Third angle orthographic projection of an object suspended in a glass box
The Front, Top, Right view in third angle plane of views are referred to as
Frontal, Profile and Horizontal view
The difference between first and third angle projection
first angle- right view on left side of front view
third angle- right view on right side of front view
3d view is called pictorial view. What are 3 views
perspective
oblique
isometric
Drawing used in architecture and construction because drawing mimics the way eyes see an object.
Front view undistorted with top and right view tapering.
Perspective view
Not common in mechanical trades because of distortion to round objects.
Front face undistorted, other sides are distorted in proportion to the angle and scale.
Oblique
Common in mechanical trades for good representation of workpiece.
Front view has 30 angle front horizontal with all three axes 120 apart.
Isometric
Object or visible line
Used to show shape of an object. Should be thick and dark.
Centre line
Show a part is symmetrical.
Line is thin, broken, made of alternating long and short dashes.
Hidden line
Some features of an object are hidden.
Line is made up of a series of medium dark short dashes.
Dimension line
Used for placement of dimension.
Thin line with an arrow on each end to indicated the distance being dimensioned.
Extension line
Pair of lines extending from an object. Signify the distance that is to be dimensioned.
Leader line
Line leads from information to a particular area.
Thin line terminating with arrow, dot or tilde.
Cutting plane
Signifies sectional view was taken.
Lines are thick, dark lines either broke or continuous with arrows at right angles
Phantom line
Shows a mating, or moving part. Line is broken made up of a long dash followed by two short dashes.
Drawings should have lettering in what font.
Upper case gothic
BC
bolt circle
BHC
bolt hole centre
BCD
bolt circle diameter
C to C
centre to centre
CTRS
centrers
D or DIA
Diameter
TYP
typical
CBORE
counterbores
CSK
countersink
Similar to counterbore but has no depth.
Main purpose to provide flat seat for head of bolt
Spotface (SFACE)
CH or CHAM
chamfers
Sizing of woodruff key
first 2 number
last 2 numbers
first 2 numbers x 1/32=width
last 2 numbers x 1/8=diameter
What angles should chamfers be?
45
What are 2 bearing types
plain
anti friction
Full section
the cutting plane is straight and goes completely through the work piece
half section
the cutting plane goes through only half the work piece, showing the inside and outside at the same time
removed section
shows cross sectional shape of a work piece. A center line is used to show where the section was taken from
revolved section
similar to a removed section, but the cross sectional shape of an object is revolved 90 degrees
broken out section
shows only a small portion of a part. a broken line is used to isolate the piece that is to be sectioned
offset section
cutting plane lines changes direction 90 degree several times to cut through features to be show in section
aligned section
cutting plane line is rotated through various angles to align all the features
