Summary

This is a simple spool adaptor I made so I can use some spools with 20mm holes in them. This fits my Flashforge Creator X Pro. It may fit other printers of similar design that have at least a 30mm hole for spool mounting.

Instructions

I printed the 30mm nut at .15mm layer height in ABS. This seemed to work good on my printer. The Spool Adaptor was printed at .1mm layer height to make sure the 1/2-13 threads inside came out nice. I would think this would also work fine in PLA.
I used a 1/2-13" X 5" bolt to hold the spool. With large spools the bolt does not have to be removed. Just slip the spool over the head of the bolt. On smaller spools like the 20mm ones I have remove the bolt, slide the bolt into the spool and screw it into the adaptor.
I thought about printing using a length of threaded rod instead of a bolt with a nut and washer on the outer end to retain the spool. Maybe even a printed tube to cover the threads of the rod so the spool would turn smoothly. But the bolt works good enough for now so I didn't bother.

Also when you first install the 1/2-13 bolt you may find it a little hard. For me I just screwed the bolt in and out a few times and it goes in nice by hand now,

Flashforge Small spool Adaptor