how to give or control the arc length/chord length dimensions and could you please explain me the how to make relation of arc length/chord length to diameter.
I am not following your question completely but let me try to help with I may be understanding.
In order to get a cord length, it is simply a distance between two points. Creo Sketcher tries to make dimensions vertical or horizontal by default, but if you click between the two points, it will dimension the diagonal.
For arc length, you select one end of the arc, hold Ctrl and click the other end... continue to hold Ctrl and select the arc, then place the dimension. This will specify the arc length rather than a linear length.
The second part of your question needs a little more explanation regarding length to diameter. I am not sure what you want to do with a relation in this regard.
I don't know if things have changed in later versions, but that procedure yields an angular dimension in WF4, not an arc length.
I hope it has changed in Creo 2, that is another good reason to upgrade.
In WF4, I have to select the arc and Edit, Convert to, Perimeter and select the dimension I want to vary to achieve the arc length (usually the angle), in order to get an arc length dimension
John, I think you are describing a perimeter dimension, which is more general that applies to chains of entities and not just to arcs.
Arc length dimensions are related to the included arc angle. To get the arc-length dimension, click one end of the arc, then click the other end, then click on the middle of the arc, then finally middle click outside of the arc and you'll get a dimension with an arc "accent" above it. You can then switch back and forth by right-clicking on the dimension and selecting "Convert to Angle / Convert to Length".
Does anyone know how to obtain the included-angle dimension for an arc directly?
As I said, the method you describe produces an arc included angle dimension in my version of WF4 (M220), not an arc length. There is no "Convert..." sub menu under the right-click options.
If it produces an arc length in Creo 2, that is a useful enhancement (possibly one of the few, if I understand most people correctly ).
As far as I have been able to ascertain, the only way to produce an arc length in WF4 is by using the Perimeter functionality, which is, as you say, more versatile than just arc lengths and therefore more tricky to use.
We need to move to a less pre-historic version, I know...
Yup! Total drag.... I think that limitation has been around since it was first introduced. There's plenty of occasions I could have used multiple ones in a sketch and instead had to make evaluate features etc. to drive a perimeter in a later sketch.