608ZZ Bearing Grease Repacking Tool

Most YouTube tutorials on "how to repack 608ZZ bearings" suggest prying off the metal shield with a knife. This damages the shield and permanently turns your 608ZZ (double-shielded) into a 608Z (single-shielded). I created this simple tool to let you thoroughly repack 608ZZ bearings with fresh grease without opening or destroying the metal shields. (The photos show 608RS bearing because I decided to publish this model AFTER I mounted 608ZZ bearings on the roller skis.) How It Works The tool consists of two parts: - The Cup: Holds the grease and snugly fits the outer ring of the bearing.

- The Plug: Fits tightly into the bearing's central hole (inner ring) to act as a handle and drive the mechanism.

Preparation & Cleaning - Remove old grease and dirt by rinsing the bearings in mineral spirits. (Tip: A small 12oz. glass jar works great—eight bearings fit nicely side by side on the bottom).

- Let the bearings fully dry before packing with fresh grease.

Step-by-Step Procedure - Load Grease: Put about 0.3 cm3 of lubricant into the Cup. (For the Super Lube Synthetic Grease in 3 oz. tube, I squeezed a bead of grease, roughly equal in length to its diameter.)

- Mount Bearing: Insert the Plug’s stem fully into the bearing's inner ring.

- Engage & Rotate: Holding the Plug in one hand and the Cup in the other, press the bearing into the Cup about halfway (3–4 mm). Start rotating the Plug while applying light pressure to push the bearing further into the Cup.

- Feel the Fill: After about 10 rotations, you will feel slightly more resistance—this indicates the grease has entered the lower chamber and reached the balls and separator. Maintaining the light pressure, continue rotating for another 10–20 rotations to push the grease through to the upper chamber.

- Wipe Excess: Remove the bearing from the Cup and wipe away external excess grease with a paper towel.

- Distribute: Using the Plug as a handle, roll the bearing back and forth on a flat surface covered with 2 or 3 layers of paper towels. Do about 100 strokes with increasing speed to evenly distribute the grease inside. Any excess forced out through the gaps between the shield and inner ring can now be wiped clean.

- Finish: Remove the Plug, add another ~0.3 cm3 of lubricant to the Cup, and repeat for your next bearing.

Print Settings - Layer Height: 0.2 mm

- Perimeters: 3

- Infill: 15% Rectilinear

Tested and printed using Sunlu PLA+ 2.0 on a Prusa Core One with a 0.4 mm nozzle. Note on Tolerances: Depending on your specific printer calibration and filament shrinkage, you may need to adjust the X/Y scale slightly so the Plug fits tightly into the inner ring, and the outer ring fits snugly into the Cup while still allowing smooth movement.