Cutting plane bent at 90 degress to show more detail on asymmetrical objects
Half Section
- Removes a quarter of the object
- Reveals half of its internal details
- All hidden lines ommitted
- Not necessary to label cutting plane
- Only half of view is cross sectioned
Revolved Section
- Shows cross-section by rotating 90 degrees
- Remains on object
Removed Section
- Shows cross section by rotating 90 degrees
- Moved to the side of object
Broken out section
- No cutting plane required
- Does not modify rest of view
Broken View
- Used for extremely large or long objects
- 2 break lines
Detailed View
-Circle cut out showing more detail of an object
-Must have scale
Sectioned Pictorials
Sketch of the object with portion missing
Do NOT Hatch!!!
Ribs
Thin parts like gaskets
Shafts or pins
Screws or nuts
Cast Iron and General Use
ANSI 31
Steel
- "striped"
- ANSI 32
Brass, Bronze, Copper
-ANSI 33
-"Road"
Lead, Zinc, Magnesium
-ANSI 37
Aluminum
ANSI 38
Crest
Peak or prominent point of a thread
Root
Bottom point at which sides of a thread meet
Flank
Thread surface that connects a crest and a root
Angle
Degrees between two flanks
Pitch
Distance between 2 adjacent crests or 2 adjacent roots
Thread length
Length of a threaded portion of a shaft
Depth
Height of a crest
Shank
Unthreaded portion between head and threads
Thread symbols
Detailed, schematic, simplified
Knurl
Pattern cut into cylindrical parts to improve gripping
Counterbored
CBORE or CB
Spotfaced
SFACE or SF
Countersunk
CSINK or CSK
Counterdrilled
CDRILL or CD
Diameter
DIA
Depth
DP
What is the standard measurement of an engineers's scale?
Inches
What is the standard measurement of a metric scale?
Millimeter
How does an architect's scale work?
Number on left of equal sign is specified by some fraction of an inch, number on the right is ALWAYS 1'-0"
Ex. 1/2 = 1'0"
Tolerance
-Range of acceptable values for a particular dimension
-The smaller the tolerance, the higher the cost of manufacturing
General Tolerance
-Applies to all dimensions of a drawing
-Often found in title block
-Normally in bilateral form
Limit form - Tolerance
Has max value over min value
Unilateral form - Tolerances
Has base value, then to the right of it has the maximum added above mimimum added
Bilateral form - Tolerances
Base diameter, then to the right it has +/- a number
Linear Fit Tolerances
How tight or how loose moving and sliding parts wll fit
Hole tolerance
LPH - SPH
- Determines cost of hole
Shaft Tolerance
LPS - SPS
- Determines cost of shaft
Allowance
SPH - LPS
-Tightest fit between two moving parts
-Does not affect cost of parts
Maximum Clearance
LPH - SPS
-Loosest fit between parts
-Does not affect cost of parts
Clearance Fit
Shaft is always smaller than hole
Line fit
Shaft is either smaller or equal to hole
Transition fit
-Shaft could be larger or smaller than hole
-Cheapest way to manufacture part
Which fit is the cheapest to manufacture a part?
Transition fit
Interference fit
-"Force fit"
-shaft always larger than hole
Geometric tolerances
-Controls level of error of shape not size
Dimensioning
Always in real world units
Do not put units by numbers
Styles for dimensioning
- Unidirectional: dimensions face same direction
- Alligned: dimensions parallel to lines
Dimension spacing
- First row: 3 letter heights away (3/8")
- Successive rows: 2 lettee heights away (1/4")
Dimensioning Cylinders
Place diameter where it appears at a rectangle
Bolt circle
When feature has repetitive holes in circular pattern
BC
Repetitive features
Ex. .75 DIA - 4 HOLES
Horizontal projection plane
-Top view
-Depth and width
Frontal projection plane
-Front view
-Height and width
Profile projection plane
-Side view
-Height and depth
Which dimensions on an orthographic projection project directly?
Height and width
What is the difference between pictorials and orthographic projections?
Orthographic projections use 2-D views to represent an object. Projection pictorials show all three directions of space in one picture
Parallel projections
Any lines that are parallel in the object are parallel in views
Perspective projections
Reproduce the effect that distant objects appear smaller than nearer objects. Lines which are parallel in nature converge towards a single point.
Types of axonometric projections
Isometric
Dimetric
Trimetric
Isometric projection
-All three angles equal 120 degrees
-H, W, and D are true size along isometric axes
-Angles must be located by coordinates
-Circles appear as ellipses on all surfaces
Dimetric projection
2 angles are equal
Trimetric
All 3 angles are different
Oblique projection
Most descriptive face of object is projected parallel to projection plane, thus appearing true size
Cavalier oblique
-Front view true shape and size
-Receding axis angle normally 30, 45, 60 degrees
-Depth dimension true size
Cabinet oblique
-Front view true shape and size
-Receding axis angle normally 30, 45, 60 degrees
-Depth dimension HALF size
General oblique
-Front view true shape and size
-Receding axis angle normally 30, 45, 60 degrees
-Depth dimension is BETWEEN full and half size
GRID Command
F7
Just a visual aid, does not print
SNAP Command
F9
Allows you to specify precise coordinates when using the mouse
ORTHO Command
Allows you to only draw in the vertical or horizontal direction
DDEDIT Command
Click on a text or dimension to be edited/changed
BHATCH command
Crosshatching
Area must be closed
How many views are required to illustrate an object?
-Depends on the object
-The minimum necessary to adequately show the object's geometry
What is the thickest line drawn in an orthographic drawing?
Visible line
Which view should be the most descriptive view?
Front view
Which dimension should be minimized in orthographic views?
Depth
What are drawing methods used to provide a clearer understanding of an object, even if orthographic rules are violated?
Conventional practices
Which type of sketch is not a pictorial?
Multi-view
What types of projections are not parallel projections?
Perspectives
In what type of oblique drawing is depth represented true size?
Cavalier
Auxiliary view
Used to represent the true size and shape of objects with sloping surfaces
In English thread notes, what represents the fit
1 for loose
2 for regular
3 tight
In English thread notes, what represents if the thread is internal or external?
A is external
B is internal
In metric thread notes, what represents the tolerance?
Numbers ranging from 3-9. The larger the number, the larger the tolerance.
In metric thread notes, what represents the fit?
Letters.
E - loose fit
G - regular fit
H - tight fit
Lowercase letters mean external
In metric thread notes, what represents the thread length?
S - short
N - normal
L - long
T or F: The force on a truss link is called an axial force
True
How do you calculate the number of joints in a 2-D truss?
L = 2 • J - 3
How do you calculate the number of joints in a 3-D truss?
L = 3 • J - 6
What are allowable loads (working loads)?
Forces to which the links can be safely subjected.
What are the two principle modes of failure?
Failure by separation and failure by deflection.
True or False. Zero-force members cannot improve the strength of a truss
False
How do you calculate arc length?
S=R•radian angle
How do you find zero force truss members.
If a joint connects only two truss members and no support reaction or external force is applied to the joint
If a joint connects only three members and two of the members are co-linear, and no support or external force is applied, then the non co-linear member is a Zero force member
In which views will circles appear as ellipses for all views?
Axonometric projections
What determines the diameter of the spotface for a spotface hole?
Left to the disgression of the machinist
In what type of sections can you show hidden lines?
Broken out sections
How do you calculate a safe loads?
External load Largest tensile
Force
--------------= --------------
Max allowable Tensile External load strength
How do you calculate the factor of safety?
Failure level Strength
------------- = --------------
actual Internal Level member force
T or F: The factor of safety is the most conservative value?
True
When calculating internal forces, what do we assume?
The the bars are in tension. Therefore, the arrows are drawn going away from joint
