C-mount extender

C-mount extension tubes of different lengths.

Update 08/2018
* Fixed thread pitch of the outer thread (was 0.75mm, corrected to 0.794mm=1/32").
* Added more tolerance (0.2mm on the thread diameter instead of 0.1mm, for each of the threads).
* Reduced model resolution in order to bring down the file size.

Printing
Because of the relatively fine threads, a layer height of 0.15mm or smaller is recommended. Obviously, for the thread to work smoothly, the dimensional accuracy has to be quite high. Over-extrusion should therefore be avoided by all means. If the threads don't fit, one can fix this by changing slicer parameters, either or both the XY scaling factor and the "Surface inset" or "Horizontal size compensation" parameter (or whatever it is called in your slicer). Be aware though that just re-scaling has different effects on the inner and outer thread; one will have more clearance, the other will have less. If you need to get more clearance for both threads, "Surface inset