Are you asking me? I don't have a current tutorial but it's not especially difficult. Work with units set to Meters and enter millimeters as meters. So for a 6mm screw, draw it as 6 meters. I use Curve Maker's Helix tool to create a helical path for the threads. For that 6mm screw and working in meters, the radius will be 3 meters and the height per turn will be 1 meter.
Then I draw the profile based on dimensions available just about anywhere. If you are modeling external threads you'll wind up drawing a face with a V-shaped notch in it. Draw this is place at the bottom of the helix. Then explode the group containing the helix.
Use Eneroth Upright Extruder to extrude the face up the helix.
As far as terminating the threads, it depends on what you need. Generally you'd draw a shape that matches the end of the screw and intersect that with the threads. For the bottom end of the external threads on this machinists jack I drew a cone and intersected it with the threads to get the chamfer. I used a similar cone on the top of the jack base for the internal threads. At the top of the screw I used a shape like you'd get with a round-nosed tool if you were turning that section of it on the lathe.
https://live.staticflickr.com/7839/40253582383_a3028d7168_z.jpg
If you are 3D printing the model, make sure you clean it up. ThomThom's Solid Inspector2, and CleanUp3 can help as can TIG's Solid Solver.
