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E112 Lesson 6 mindmap - Coggle Diagram

- - - - A circle is dimensioned by its diameter, an arc by its radius and a hole by its centerlines
    - - Dimension should start with "R". This is to show a radius dimensioned with the centre of the radius located on the drawing. This also shows how to dimension radii which do not need their centres located, e.g Curves,arc, etc.
    - - To dimension multiple same dimensions, use N x dimensions.This is because dimensions should not be duplicated
    - - Placing the arrow heads outside of the extension line instead of between it
    - - Uses both chain and parallel dimensioning
    - - Should only be used if the function of the object would not be affected by the accumulation of the tolorence
    - - Simplifies parallel dimensions in order to reduce the space used
    - - Consist of several dimensions originating from a common reference surface also known also datum ( All measurements starts from the same edge)
    - - Marked with a curved dimension line and a degree symbol
  - - - The united mm is not always written down, shows the length of the drawing, and is placed at the bottom corner of the drawing
    - - Defines how much the dimension is allow to deviate
    - - The arrowhead at the end of the line
    - - Used to established the size of the object, do not touch the object,extend slightly pass the extension line
    - - The gap between the object and the extension line
- - - - If there is sufficient clearance for the shaft to interface with the hole, it is a clearance fit, as the shaft can enter the hole easily. Happens when the hole is bigger than the shaft. When there is still be an allowance for two parts to move, such as in a door hinge
    - - Happens when the shaft is bigger than the hole. When it is difficult to move or remove the two interfacing parts. Usually, a lot of force is needed to remove the two parts.
- - - - allowed to vary in two directions from the specified dimension. Both directions need not vary by the same amount.
    - - the upper and lower limits of the dimension are specified
    - - allowed to vary in only one direction