I am a jewelry designer and I find that Rhino is excellent for doing
mechanicals of jewelry designs with the added plus (for you) of a lot
of similar to identical commands as in AutoCAD. I prefer this
program for mechanical drawing as the curve commands are so simple
and the trim and snaps are so quick and uncomplicated.
Corel Draw is also used for mechanical drawing as well as more
freehand sketching and has a bezier tool as well. In this program
you can also incorporate bitmaps into your designs if you want. Use
of a graphics tablet with this program can be very useful for
For real freehand sketching, if you want to do that on the computer
as well, Corel Painter used with a graphics tablet is very powerful.
This program has the additional benefit of an interactive painterly
coloring of your sketch a la traditional design rendering. One
option with this program is the interactive coloring in of line art
imported from programs like Rhino and Corel Draw.
I hope this helps you out.