Let's make one thread of a jack screw.

Set up the grid.

Create a 20x20 closed spline at X -80.

Lathe it as below.

Delete the spline and the back half of the circle.

We want thread offset to be one threadspace. Height=20. OffsetSteps=10. Set grid to H/O.

Disable X. Select the points as below. Move them one gridsnap up.

Select the points as below. Move them one gridsnap up.

.....ditto

.....ditto....

.....ditto...

.....ditto five more times....

Copy and paste the threadhalf. Then rotate it 180 degrees on Y.

Set grid back to 10. Move the second threadhalf down 2 gridsnaps.

Select both threadhalves. Join solids.

Select the points below. Merge points.