Drawing standards and conventions Flashcards
What are three advantages of using British drawing standards?
- Standards used in the drawings are consistent across the world and are universally understood.
- The common drawing symbols and conventions have been designed so that drawing features such as screw threads are simplified making them quicker to draw and easier to understand.
- Applying world wide drawing standards helps break through language barriers; important in supporting cross border engineering projects.
Why is scaling used in drawings and what are examples of different types of scales?
Scaling is used in drawings because at some point a drawing needs to be printed in paper or viewed in its entirety on a screen. The choice of scale is determined by the size of the object so that the clarity of detail is obtained.
Full size: 1:1
Enlargement: 2:1, 5:1, 10:1, 20:1, 50:1
Reduction: 1:2, 1:5, 1:10, 1:20, 1:50
What is third angle projection?
Orthographic views are set out using the third-angle projection layout. The third angle projection symbol must always be present to accompany an orthographic drawing.
The plane’s directly above and the elevation and the end elation is drawn a to the right.
What are the principles of dimensioning?
- Units should not be shown on the dimensions, the mm unit should be recorded in the title block and applies to all dimensions with the exception of angles (degree symbol).
- A drawing should not be over dimensioned and every dimension should only be shown once.
- Dimensions must be neat and clear and understandable.
- Dimension arrows should be small and slim, projection/leader lines shouldn’t touch the drawing.
What is in a basic title box?
Name
Project name
Date
Scale
Measurement/size
Page number
Third angle projection symbol
Tolerance E.g. ( +/- 0.25)
What is a countersunk hole?
A countersunk hole, is a conical shape at the top that allows a screw or bolt head to sit flush with the surface.
What is a blind hole?
A blind hole is a hole that does not go all the way through the material; it has a bottom but is not visible from the other side. Blind holes are often used when you don’t want the hole to penetrate through the material for aesthetic reasons or to maintain structural integrity.
What is an assembly drawing and what are examples of when to use them?
Products that have more than one component need assembled. Assembly drawings gives information to the manufacturers about the product assembly. They can also provide information about home assembly and are often used in information brochures and leaflets. Rendered assemblies can be used in promotional publications.
What are sections?
Slicing a product to show the inside of the assembly to show how the components interact. Sectional views are very technical and are normally to complex for a consumer in instruction brochures.
What is an exploded view and when should you use them?
When components of an assembly are separated along an axis to show how parts fit together and how a product is assembled. They are used in promotional, instructional and assembly publications to support the consumer.
What is a tolerance and why are they required in assemblies… interference?
When products are manufactured, component parts are made separately before being assembled. If a component isn’t correctly sized, it won’t fit with the rest. A manufacturing tolerance is added to the dimension is used to set the limits of a permissible manufacturing error in sizes that will still allow components to be assembled.
Requirement for assemblies:
If both a good and a post insert are exactly the same size, the insert will not fit inside the hole which is called the interference. The means the dimensions would be tolerance.
What are two reasons for applying manufacturing tolerances?
To ensure that parts can assemble correctly.
To enable interchangeability of parts, for instance when a part wears out and needs replaced, the new part should fit without modification.
What is a functional tolerance?
They are essential to the component being manufactured.
It is applied to dimensions directly affect the function of the product e.g. dimensions that enable a product to assemble or enable moving parts to move. Functional tolerances are noted beside the dimension of the drawings.
What is a non-functional tolerance?
They do not play a critical role in the function of a part.
They are applied to all other dimensions that are not critical to the functioning of a product. They are normally found in a title box.
What is first angle projection?
It is the opposite of third angle projection, the plan is shown below the elevation and the right hand view is shown on the left hand side.
