How to edit the Length of a Part, or to edit a Dimension
To edit the length of a Part is one of the most fundamental actions you must do to model kinematicchains.
You must use the PartEditor to edit a Part.
Key Learnings
•  To edit a Part you must select the Part, and open the PartEditor. 
•  You MUST [deselect] Add Dimension before you can edit a Dimension. 
•  Doubleclick the arrowhead or extension line of a dimension to open the Dimension dialog. 
•  Nothing will happen if you doubleclick the dimension value (the number itself). 

Start the PartEditor.
See here: How to start the PartEditor
For example:
STEP 1:  DoubleClick the PartOutline of the Part you want to edit 


You are now using the PartEditor.
To edit a dimension:
STEP 2:  DoubleClick the arrowhead of the dimension 


STEP 3:  Enter a new dimension in the Dimension dialogbox 
•  You can type in a new dimension in the box 
You must use the ENTER key to confirm the new dimension before you use the 'OK' button.
 or 
•  Use the spinbox tool 


 or 
STEP 3:  Rightclick the Dimension Value and select 'Round' 
The Dimension changes to the nearest value that is exactly divisible by the 'SpinIncrement'.
In this example, the SpinIncrement = 10.
Thus the new dimension will round to become 130.


 or 
STEP 3:  Enter an equation into the data box. Use the Enter key to apply the equation. 
•  Simple Arithmetic: +, –, *, ∕ 
•  Trigonometric: Angle in Radians 
o  ArcSin(), ArcCos(), ArcTan2( ; ) 
