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Dimensions, Tolerances and Assemblies - Coggle Diagram
Dimensions, Tolerances and Assemblies
Dimensioning
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Chain Dimensioning
Should only be used if the function of the object would not be affected by the accumulation of tolerances
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Dimensioning of Circle, Arc and Hole
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Dimensioning Angles
Its marked with a curved dimension line, and has the degree symbol
Rules of Dimensioning
Dimensions should not be duplicated, i.e. same dimension should not be repeated on different views, or the same information need not be given in two different ways
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Dimension lines, extension lines and object outlines should not cross or overlap
Tolerances
Why is it important?
If tolerance is not given, exact measurement of the parts must be made. Rejection rate will be very high and is not realistic.
The range of tolerance will translate into the manufacturing method needed, since different manufacturing method has different degree of tolerance.
Same parts can be made from different companies and they have to be interchangeable. Tolerance ensures good quality control for parts from different companies.
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Types of tolerances
Bilateral Tolerance: allowed to vary in two directions from the specified dimension. Both directions need not vary by the same amount.
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Calculating Tolerances
Tolerance is defined as the difference between the upper limit of a dimension and the lower limit of the dimension. Its formula is given by:
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Assemblies
In clearance fit, there would still be an allowance for two parts to move, such as in a door hinge
In interference fit, it would be difficult to move (or remove) the two interfacing parts. Usually, a lot of force is needed to remove the two parts. Examples are shafts that are fitted through bearings, so that the shaft does not slip
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Revolute Joint : Has a single rotational degree of freedom, much like a hinge
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