Parameteric 1x1 Gridfinity solder spool holder using a 608 bearing and M8 bolt to achieve unlimited spool width.

While other holders either build a fork around the spool, limiting its maximum width, or insert the bearing into the spool hole, adding constrains on compatible spool designs, this one uses a M8 bolt (potentially cut to size) as an axle, a locknut to secure it in place, and a bearing to reduce friction. In other words, less plastic, more commodity items you have a bunch of already.

Print this the holder face down, adding supports for that end of the Gridfinity interface.

The code can be found here, in a fork of cq_gridfinity. You can edit the variables at the bottom to adjust for larger spools, other bearings, etc.