Dimension, Tolerances & Assemblies
Dimension
How
Dimension Text
Tolerances
Dimension Lines
Extension Line
Extension Line Offset
click to edit
What?
Units
Dimension Text displays the size of the object
Usually in mm (Unit not indicated in the text but it's shown in the title block)
What?
By how much?
±0.2 Is the tolerance
By how much the dimension is deviated
What
Arrow Head on each end
What
It continue or extend from surface of the object and establish the size of the dimension.
Extension Lines do not touch the object.
What
Gap between the object surface and the extension line
Why
so that it is not confused with the visible line on the model
Types
Parallel
What
Consist of several dimensions originating from a common reference surface
Superimposed running
Why
What
Simplifies parallel dimensions in order
Reduce space used on a drawing
Chain
What
When
Use only if the function of the object would not be affected by the accumulation of the tolerances.
Combined
What
Uses both chain and parallel dimensioning
Dimensioning small feature
How
Place arrow head outside the extension line
What
Dimensioning of Multiple Features
What
How
Dimension multiple same dimensions, use N x Dimensions.
Radius
What
Arc, Circle and Hole
What
How
Circle is dimensioned by its diameter.
Arc is dimensioned by its radius
Holes are located by their centerlines
Angles
What
How
Mark using curved dimension line and has the degree symbol
Tolerance
Types
Bilateral
Unilateral
Limit
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
the upper and lower limits of the dimension are specified
Calculate
Tolerance = Upper Limit - Lower Limit
Clearance Fit
Assemblies
What
an air space or clearance which exists between the shaft and holes
Interference Fit
.
What
fit between two parts in which the external dimension of one part slightly exceeds the internal dimension of the part
Joints
Types
Rigid
Revolute
Sldier
Cylindrical
Pin Slot
Planer
Ball
What
Fixes two Component to one another
What
Has a single rotational degree of freedom, much like a hinge.