Centauri Carbon replacement spool holder

Replaces the original small diameter plastic spool holder on the Centauri Carbon with a 5/16" or 8mm threaded shaft for use with a ball bearing spool holder. This adapter was designed to us in conjunction with my remix of PurchenZuPoden's Universal Filament Spool Holder.

The ball bearing spool holders can be found here: 

• my remix: https://www.printables.com/model/1347214-low-profile-filament-spool-holder 
•  of https://www.printables.com/model/65651-universal-filament-spool-holder

The Centarui Carbon's spool holder mounts on the printer's right side with a bayonet type twist-lock. The original spool holder  locks in place with a left handed twist. After printing the adapter with a similar left-handed twist-lock, I realized that there was nothing in the mounting fixture on the printer that forced the left handed twist. I have therefore included both left-handed and right-handed twist lock adapter models. You can use whatever you're most comfortable with. Additionally, here in the USA 5/16" threaded rods are more generally available in the big-box stores than 8mm. I've included STL's for both 8mm and 5/16". I've only the printed the 5/16" versions because that's what I had on hand.

I've found that using a ball bearing holder, the spool turns very smoothly,  and for some stiff filaments, too easily. To control the rotation of the spool, I use the included Magnetic Spool Drag model to press against the rim of the spool. The spool drag as pockets to super glue in 3 12x3mm magnetics. I'm currently only using 2 of the magnets and seems to work fine. Add the third magnet if you want a little more grip to the printer side wall. 

UPDATE July 18, 2025

Uploaded new STL's for all 4 implementations (inch & metric, left-hand & right-hand twist) with slightly steeper pitch to the bayonet twist to fit tighter to the side of the printer. 

Alternate hardware: Use a hex bolt (5/16" x 4" or 8mm x 100mm, or longer) inlace of the threaded rod and one of the nuts. Added a picture showing both options - 5/16" threaded rod and 8mm bolt.

Printing notes:

I printed with .2 layers.

Supports are required  for the the bayonet groove overhang and for the cylindrical recess In the base.

 I printed in PETG which I think will last longer than PLA with the weight of a filament spool hanging on it. That said, I have used a similar design printed in PLA+ on an Ender 3 V2 for the last 2+ years without any problems.

Required hardware:

(1) shaft - 8mm dia x 100mm - or - 5/16" dia x 4" threaded rod

(2) M8 or 5/16" hex nut

Assembly:

Screw one of the nuts onto the very end of the threaded shaft.

Insert the shaft into the adapter so that the nut sits in the hex pocket of the adapter. Tighten the other nut into the cylindrical recess in the out collar of the adapter. You'll need a wrench with thin jaws to grab the nut down inside the recess. You want this to be tightened securely, not just finger tight.

Push the bayonet end of the adapter into the side mount fixture on the printer and lock it in place with a right or left handed twist depending on the model selected.

Pro Tip:

For fine control of spool rotation stick a small piece of adhesive backed foam on the MagneticSpoolDrag.