>How can i use AutoCad or AutoCAD mechanical to draw a large auger? Do i need to use an autoLISP script from somewhere or is there a built in function?
You probably need MDT or Inventor. AutoCAD and Mechanical are not really 3D modelers. There are a few 3D "helix" and "spiral" lisp routines for ACAD floating around, but I have not seen particularly good results. Try a search on these terms to find them.
Do you have some specs for your auger?