There are reasons to "Adequately Constrain" vs "Fully" Constraining a drawing.
Adaquately Constrain means that you still have flexiblity in the sketch ( like using a driven dimension, for an adaptive part).
It can also mean your lazy and don't want to constrain something thats not going to effect your Sketch (like a centerline for a revolve).
Essentially your not finishing the Sketch for one reason or another. (as the others have said its a good idea to Fully Constrain your Sketches if you do not intend it to be adaptive)
Fully Constraining the drawing means NOTHING moves there is NO Flexibity.
( although you could still have driven dimensions to pull out duplicate data like bolt hole circles, that also require a square pattern, but not really the point)
So its "impossible" (more like highly improbable) for the part to change on its own. ( I have seen contraint failures, normally from projected edges or faces changing, moving the end of part tool can destroy just as well as it can fix parts)
A fully contrained Sketch can't be adaptive, just as an Adapitive sketch can't be fully constrained.
So it depends solely on how you intend to use the sketch.
Hopefully that gets you going,
James
James Alger
(I'm on several hundred posts as "algerj")
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