Microscope objective lenses exhibit a 0.8 x 1/36 inch RMS thread:
https://en.wikipedia.org/wiki/Screw_thread
https://threadingtoolsguide.com/en/blog/thread-in-microscopy-the-microscope-object-thread/

At first it seemed difficult to print a microscope RMS nut thread on FDM 3D-printers:

• FDM 3D-printers print horizontal layers of typically 0.3 mm height (or less). But threads are inclined, not horizontal.
• This is usually not a problem with coarse threads e.g. M12 x 1.25, see my
  https://www.thingiverse.com/thing:5404145
  But with threads of 0.7 mm lead? Mission impossible?

Solution:

• On each horizontal FDM layer print only the intersection between the FDM layer and the thread (within a certain vertical allwance).

I did not conduct a patent search. If there is a patent then you have to honor it. If there is none then my idea is in the public domain.

As always I include the OpenSCAD source file for you to adapt and improve. 

The enclosed Microscope_RMS_thread_ring.stl file is meant as examples for your testing and is assuming a layer height of 0.3 mm. You may adapt the layer height and other parameters (e.g. vertical allowance) in the OpenSCAD source file.

The enclosed Microscope_RMS_thread.stl file (also assuming 0.3 mm layer height) may be integrated into your CAD design if you are using a CAD tool other than OpenSCAD.

See also my other designs:
https://www.thingiverse.com/thinger13/designs