>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.
The program is Autodesk Inventor not Autocad.
When you are ready to give it a try you might want to post the specs at the Inventor forum:
This isn't exactly what you are doing but is related. Check the Worm.zip
Pull down the red End Of Part marker (usually referred to as EOP). Doing a coil is fairy trivial in Inventor.