LESSON 6
dimensions
Parallel Dimensioning
consists of several dimensions originating from a common reference surface
Superimposed Running
simplifies parallel dimensions in order to reduce the space used on a drawing
Chain Dimensioning
should only be used if the function of the object would not be affected by the accumulation of the tolerances
Combined Dimensioning
uses both chain and parallel dimensioning
Dimensioning Small Features
placing arrow heads between the extension lines may make the dimension very difficult to read. Arrow heads can be placed outside the extension lines instead
Dimensioning of Radius
shows a radius dimensioned with the centre of the radius located on the drawing or dimension radii which do not need their centres located
Dimensioning of Circle, Arc, and Hole
click to edit
A circle is dimensioned by its diameter.
An arc is dimensioned by its radius.
Holes are located by their centerlines
Dimensioning Angles
marked with degree symbols
tolerance
Bilateral Tolerance
allowed to vary in two directions from the specified dimension
both directions need not vary by the same amount
Unilateral Tolerance
allowed to vary in only one direction
Limit Tolerance
the upper and lower limits of the dimension are specified
fits
clearance fit
there would still be an allowance for two parts to move
interference fit
difficult to move (or remove) the two interfacing parts