A lot of sheet metal parts
require holes patterns to be equally spaced. There is a real easy solution
to do this. First, I created a simple sketch with points to indicate the
center of the holes or any other feature that you need evenly spaced. I set
a specific distance from the end of the part that must be maintained.
Your first instinct may be to dimension the centerpoints, as shown below.
But when the part length is changed, the centerpoints are no longer spaced correctly.
Rather than using dimensions, just create three construction lines. I
changed the line color and thickness so that you can see that it is not just
one centerline, but three separate lines. Then, all you have to do is
Ctrl+select your three construction lines and add an [b]Equal[/b] relation.
Now, when the part length is changed, the centerpoints remain evenly spaced.