Engineering drawings Flashcards
What is the purpose of an engineering drawing?
> Convey function
For manufacturing instructions
For inspections
Tolerances:
Define tolerances
The acceptable variability in the dimensions that allow the product to still work
Tolerances:
Define limits
Maximum and minimum dimensions
Tolerances:
What is a bilateral tolerance?
This is where there are equal limits above and below the nominal distance
Tolerances:
If there is no tolerance specified on the diagram, where will it be found?
In the title block
Tolerances:
How are tolerances shown on the drawing?
As the upper tolerance above the lower tolerance
Tolerances:
What is a unilateral tolerance?
This when there is no deviation from the nominal value
Tolerances:
What is tolerance accumulation/chaining?
This is when tolerances in series with each other sum together to produce an overall very large tolerance.
Tolerances:
What is datum baseline dimensioning?
This is where all dimensions are drawn relative to a reference plane/point
Tolerances:
What type of dimensioning scheme should be used for engineering drawings?
Datum baseline dimensioning
Tolerances:
What is direct dimensioning?
This is when a specific dimension is drawn on an engineering drawing
Tolerances:
When sampling tolerances, how do they statistically graph?
As normal distribution
Tolerances:
What is the equation for the standard deviation of chained dimensions?
σtotal = √(σ1^2 + σ2^2 + … + σ3^2)
Tolerances:
What is the standard method of calculating suitable ± values for a dimension?
±3σ
Engineering drawings:
What is a design scheme?
A drawing with notes, drawings and illustration that may only be understandable to the designer
Engineering drawings:
What is a design layout?
> A design showing the overall product and all its parts assembled
Drawn in orthographic projection
Engineering drawings:
What is a detailed drawing?
> Drawn in orthographic projection
Unambiguous
Has a border and title block etc
Menu instruction
Engineering drawings:
What is an assembly drawing?
> Orthographic drawing
Shows how components are fitted together
List of parts (called bill of components)
Engineering drawings:
What is an assembly process drawing?
> Isometric sketch
Shows how it is assembled
No dimensions
Engineering drawings:
What is an installation drawing?
> Shows measurements of the overall package
> Orthographic drawing
Projection systems: For the grid: x1 x2 y1 y2 What is found in each position for a first angle orthographic drawing?
x1 = End x2 = Front y1 = NOTHING y2 = Plan
Projection systems: For the grid: x1 x2 y1 y2 What is found in each position for a first angle orthographic drawing?
x1 = Plan x2 = NOTHING y1 = Front y2 = End
Projection systems:
What is an isometric drawing?
> Drawing a 3D object on a 2D paper
> 2 Receding axes @30°
Projection systems:
What is an Oblique drawing?
> Drawing a 3D object on a 2D paper
> 1 Receding axes @60° to horizontal
Projection systems:
What is a perspective drawing?
This is where you have a horizon line and point and you draw to the horizon
LIKE GCSE DT
Limits and fits:
What are the 3 types of fits for a shaft and hole? What are the features of each one?
Clearance fit - Shaft < Hole
Interference fit - Shaft > Hole
Traditional fit
Limits and fits:
How can you assemble an interference fit?
Can be assembled by changing the temperature of the parts
Limits and fits:
What is the format of an ISO fit code?
H7 / g6
H7 = Hole tolerance
g6 = Shaft tolerance
Use the table to work out the tolerance values (±)
