If any program could convert *.ptn files to *.ckd, it would be the CADKEY from which both of these file type originate. We haven't found any other capable of this conversion.
Convert CADKEY pattern to CADKEY design.
We found one software available in the database for this conversion.
Microsoft Windows software - convert ptn to ckd on Windows
A program used for modeling CAD 3D wireframes
Convert from ptn file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.