Hi Ravi,
Though drawing for a sheet-metal can be generalized. Except for 3D Part Modelling, I've rarely found much of practice drawings say on Sheet-Metal or even Surfacing. You need to work these out yourself.
For Sheet-Metal there are various books that covers the tools and their basics (basically same in all Sheet-Metal S/W).
You can try archive of Sheet-Metal-Guy here: https://web.archive.org/web/20070606123016/http://www.sheetmetalguy.com/
Regards - Jitesh