Thread Call Outs: - Do not use them in your designs!
This applies to Solidworks in particular but may be applicable to other CAD programs when designing a part for 3D printing.
When you add a thread call out in Solidworks it does not model the thread but adds an infinitely thin skin inside which is call the thread. This is so there is the possibility of using it in CAM software to associate the hole with a thread. This is a nightmare for 3D printing!
Build prep software (particularly HP MJF Smartstream) will see this infinitely thin shell in the part and try and fix it. The fix invariably is incorrect and very easy for the operator to miss on a complex part. The fix will normally skin over the hole and close it entirely, which is hardly helpful!
In place of call outs for 3D printed parts just model the pilot hole (to bottom tolerance) and use a text label for the drawing. It is useful for the text label to highlight the thread is added as a post process. This is a big help as threads can also be modelled into parts and highlights the post-process to the operator.
Please note also that a call out does not model a thread! If you are modelling a thread to be printed in place then make sure your CAD program is set to fully model the thread not to simply call it out.
Please see TN: xxx on Modelling threads directly into parts for 3D Printing.