In Reply to: rough threads posted by Bob M on 03/18/01 at 8:33 AM:
The 2 major factors I usually suggest is having the proper helix angle due to the pitch and diameter of thread so it doesn't rub, and the length in front of the part that you start at to allow the "ramp up" of the ballscrew and spindle.
If using a "laydown" threading system, there is an angled anvil under the insert. This anvil come in various angles to achieve the proper helix so the the insert doesn't rub between the pitch.
Check out my webpage for the correct angles and a calculator to find the distance needed depending on spindle speed and threads per inch.