USS Drybox LEFT-Side Drill Jig for Prusa CORE One / CORE One+ (magnetic, factory-matched)

What this is

The CORE One+ ships ready for the Prusa USS Drybox on the right side only. This magnetic drill-marking jig lets you mount Prusa's own universal puck and spool holder on the left side, in the same place as the factory right side, without measuring anything.

Set the jig in the left side recess, push it into the corner, punch four marks, and drill. That's it.

• Factory-matched position. The 26 × 26 mm hole pattern and its height and fore-aft position come from Prusa's own CAD: the CORE One assembly STEP and the universal puck. On the left panel, each hole sits within 0.1 mm of the same distance to the recess walls as the factory holes on the right panel.

• No measuring. Two pads sit on the recess bottom wall and one on the front wall. The pad faces are cut to the walls' 5° and 20° slopes. Five magnets only hold it flat against the panel.

• No glue, no print pause. 5 × Ø6×3 mm magnets press in from the top after printing. Each pocket has a lead-in, a 0.6 mm stop and a push-out hole for getting the magnet back out.

• Hard to fit wrong. LEFT SIDE / FRONT → / TOP ↑ and hole numbers 1–4 are engraved in. Upside down, the pads can't seat.

• Light. About 22 g of PLA in about 55 min on a CORE One with a 0.4 high-flow nozzle. No supports.

What you need

• Prusa USS Drybox, plus a universal puck and universal spool holder for the left side. Print them from Prusa's USS Drybox printable accessories (the "universal spool holder parts").

• 5 × West3D 6 mm × 3 mm round neodymium magnets (N52, nickel plated; what I used, from the 30-pack)

• 4 × M3×8 button head screws (ISO 7380). Don't go longer than M3×10.

• A 1/8" (3.2 mm) transfer punch or a 3 mm punch, and a hammer

• Drill bits Ø2 and Ø3.4 mm, a deburring tool, and a wood block to support the panel

Print settings

• PLA (stiffer) or PETG, 0.20 mm layers, 4 perimeters, 30 % gyroid, 5 top / 4 bottom layers, no supports, no brim.

• Print it flat, as oriented. The face on the bed goes against the panel.

• The included 3MF files contain these settings for the CORE One/+ HF0.4.

• Print the fit coupon first (6 g, about 18 min). It tells you which jig variant to print.

Which file?

• USS_left_jig_fit_coupon: 5 magnet pockets (5.95 / 6.05 / 6.15 / 6.25 / 6.35 mm) and 3 punch bores (3.2 / 3.3 / 3.4 mm).

• USS_left_drill_jig_pocket_X.XX: the jig. Choose the pocket size your coupon says. 6.15 is the default.

• STEP files, a dimensioned hole drawing (PDF) and the parametric CadQuery source are included, so you can change the pocket or bore size.

Install instructions

1. Coupon. Press a magnet into each pocket with something flat. Pick the smallest pocket where the magnet seats fully on the stop without cracking the wall and stays put when you shake it upside down. Check your punch in the bores: it should slide with no visible play.

2. Magnets. Print the matching jig and press in all 5 magnets from the top until they bottom out.

3. Check your panel. On the printer, measure:

   • the left recess depth, flange face to floor: should be 67 ± 1 mm;

   • the floor width between the front and rear walls, right at the floor: should be 240 ± 1 mm.

   If either is off, stop and leave a comment with your numbers.

4. Seat test. Put the jig in the left recess with the bottom pads on the bottom wall, then slide it toward the front until the front pad touches. It must not rock, all three pads must touch (slip a piece of paper under each), and LEFT SIDE / FRONT → / TOP ↑ must read correctly.

5. Repeatability. Mark the four bores lightly with a fine pen. Remove and re-seat the jig three times; the marks must stay centred.

6. Dry fit the drybox. Hold the puck over the marks, then the spool holder and the loaded drybox. Check clearance to the bottom lip, the carry handle and the door at full opening, and plan your PTFE route. The filament sensor is on the right side, so you need a long PTFE tube over the top.

7. Remove the panel. Power off and unplug. Remove the left side panel and check its inside face for anything near the hole area.

8. Mark. Lay the panel outside-up on a bench, with a wood block filling the space under the recess floor. Seat the jig against the bottom and front walls, tap all four marks through the guides, then remove the jig.

9. Drill. Check the marks: the sides should be 26.0 mm apart and the diagonals 36.8 mm. Drill a Ø2 pilot, then Ø3.4. Deburr both sides; an inside burr would lift the screw head toward the bed. Clean up all chips with a magnet. Don't tap the steel.

10. Mount. Screw the puck on with 4 × M3×8 from inside the panel; they thread into the puck's pilot holes, like the factory right side. Reinstall the panel. Jog Z slowly through full travel while watching the screw heads at the bed's left edge. Then lock in the spool holder and the drybox.

Hole positions (if you prefer measuring)

Measured from the inside face of the recess front wall (B) and bottom wall (A), at floor level, viewed from outside:

• Hole 1 (upper rear): B 135.30, A 125.60

• Hole 2 (upper front): B 109.30, A 125.60

• Hole 3 (lower rear): B 135.30, A 99.60

• Hole 4 (lower front): B 109.30, A 99.60

• Spool axis: B 122.30, A 112.60

The full drawing is in the PDF. The walls are drafted, so use the jig rather than a tape measure if you can.

Notes

• The left recess is 67 mm deep (the right is 80), so the puck sits 13 mm further out. The walls are in the same place relative to each recess floor, so the drybox gets the same room as on the right.

• Prusa doesn't publish drybox dimensions. That's why step 6 is a real dry fit.

• Made with Prusa's CAD (CORE One assembly, universal puck R1). This jig doesn't include or modify any Prusa parts.

If you print or install it, please post a make and leave your panel measurements from step 3 in a comment. It helps everyone confirm the fit on the CORE One+ and on Gen 1 and Gen 2 panels. 🧡