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Dimensions & Tolerance - Coggle Diagram
Dimensions & Tolerance
Dimensions in Drawings
Types of Dimensioning
- Superimposed Running Dimensioning
Simplified parallel dimensions in order to reduce the space used on a drawing
- Parallel Dimensioning (Datum Dimensioning) Consists of several dimensions originating from a common reference surface (also known as datum)
- Chain Dimensioning Only be used if the function of the object would bot be affected by the accumulations of the tolerances.
- Combined Dimensioning Uses both chain and parallel dimensioning.
- Dimensioning Small Features
Arrow heads be placed outside the extension lines instead
- Dimensioning of Multiple Features
To dimension multiple same dimensions, use N x Dimension
- Dimensioning of Radius
Radical dimensioning starting with "R"
a) shows a radius dimensioned with the centre of the radius located on the drawing
b) shows how to dimension radii which do not need their centres locating
- Dimensioning of Circle, Arc and Hole
A circle is dimensioned by its diameter
An arc is dimensioned by its radius
Holes are located by their centrelines
- Dimensioning Angles
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
- Avoid dimensioning to hidden lines and features
-Dimension lines, extension lines and object outlines should not cross or overlap
Tolerance
The Importance of Tolerance:
Tolerances account for manufacturing variations, ensuring parts fit and function despite slight differences from exact dimensions.
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 Tolerance
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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