I wanna say a huge thank to user iRupert | Published - MakerWorld who provided me .step file of the working thread design for stock spool holder which comes together with Bambu lab A1 printer.

Thread is 2,2 * 19 mm (unfortunately not standardized one).

I am sharing with you these 2 files for your customization project of printers:

File 1 - thread

File 2 - thread with an arrow - will be up, when you screw it into holder.

If it is not working for you, you can try the second version and adjust it in CAD software (sketch in the attachment box) with pitch 2,25 mm (rest is in the picture in mm - this was provided by a user serrum | Published - MakerWorld - thank you too!)