oh this is awesome.. I didn't know about them! I unfortunately don't have found any dual rotaries like above.

Quote Originally Posted by oic-u3d2 View Post
Did you have one in mind or an example you could show us?
If you're looking for some typical knobs and other hardware, McMaster-Carr's website has CAD files for a lot of their catalog.
Usually, if I can't find dimensions but i can find some good pictures that show a side or a top view - I'm not above holding a ruler up to the computer screen and measuring the longest side, making up a Scale Factor and modeling it from that. It's best to use the longest dimension..

(Final Size you decide) / (Measured longest side) = (Scale Factor)

From there, keep measuring and multiply by the Scale Factor to get the rest of the dimensions - some extrapolation may be required...