Try with beam (or even 3 beams) as in the referenced thread about bolt modeling approaches: Simplified bolt connection with beam element and rigid constraints - #104 by FEAnalyst
I wouldn’t use springs if preload is needed because it can only work with some tedious workarounds.
To be honest, even beams are problematic for bolt modeling in CalculiX. Simplified solid bolt models (3 cylinders) are the best approach in this software.