Filament Drybox Hygrometer Holder

This holder is designed for my filament drybox. It mounts directly to the filament feed-out fittings on the box.

Holder Parts and Accessories

Holder

The set includes:

•  Inner part
•  Outer part
•  Drilling template with ⌀3 mm holes
•  Drilling template with ⌀12 mm holes

Hygrometer

The holder fits both common small round hygrometers:

• Clips on top and bottom
• Clips at an angle

I bought mine from Amazon and AliExpress. Bambu Lab also sells similar meters. Meters with top and bottom clips tend to have better displays.

Connector

The holder is secured with two push-in bulkhead connectors for ⌀4 mm tubing. I purchased mine from AliExpress, where they’re sold as "PM-4 copper nickel". Connector details:

• Outer body diameter: ⌀11.8 mm
• Length: 29 mm
• Nut width: 14 mm

Tubing

You also need ⌀4 mm PTFE tubing. I purchased mine from AliExpress.

Drilling with Template

Note!

• Upper holes — required for the hygrometer holder and filament feed-out.
• Lower holes — optional extra pass-throughs for leftover filament.

Hole spacing

• Hole pairs: 80 mm apart
• Lower pair: 25 mm from the bottom edge
• Upper pair: 170 mm from the bottom edge

Steps

1. Place the box upside down and position the template.
2. If you use the ⌀3 mm template, mark the hole locations with an awl or drill through with a ⌀3 mm bit. If you use the ⌀12 mm template, you can drill the final holes directly.
3. Drill the final holes with a ⌀12 mm drill bit. A brad-point bit is the best choice, with an auger bit as a close second. Both have a centering tip and sharp cutting edges. 
   • Let the drill bit cut naturally—don’t force it.
   • Support the wall from inside the box to prevent tear-out.
   • Clean edges with a metal bit or utility knife

Hygrometer Assembly

1. Insert the bulkhead connectors into the outer part so no threads are visible outside.
2. If using sealant (e.g., silicone), apply it around the base of the threads on the back side.
3. Place the hygrometer into the inner part.
4. Assemble both parts to the box.
5. Tighten with a 14 mm spanner or similar tool—do not overtighten.

Tubing assembly

1. Insert bulkhead connectors into the lower holes.
2. Cut two 24 cm long ⌀4 mm PTFE tubes to connect upper and lower connectors.
3. Cut two 12 cm guide tubes inside the box to direct leftover filament neatly around the spool.
4. Cut two 3 cm long tubes inside the box to help protect the upper fittings from wear.