Rebuild a 3D Printer Axis: Bearings, Bushings, and Shaft Supports

A 3D printer axis that rattles, binds, or has play in it will never print straight, no matter how well you tune the slicer. The fix is mechanical: new bushings, solid shaft supports, and fresh bearings where they belong. This guide covers the rebuild.

Parts list

LM8UU / LM6UU linear ball bushings — the sliding part of the axis. SK8 / SK10 / SK12 / SK16 linear shaft supports — hold the shaft ends rigid. 608ZZ / 608RS ball bearings — idlers and pulleys. F623ZZ / F624ZZ / F625ZZ flanged ball bearings — housings where the flange does the retaining. M3 brass heat-set threaded inserts and the M3 stainless steel screw kit for printed brackets and mounts.

How the parts fit together

The linear bushings glide along the round shafts — LM8UU for 8mm shafts (8mm bore, 15mm outside diameter, 24mm long) or LM6UU for 6mm shafts (6mm bore, 12mm outside diameter, 19mm long). The recirculating ball design lets the bushing glide with minimal play. The shaft supports hold the ends of the shaft: each support bolts to the frame, with a clamping slot that grips the shaft firmly while still letting it be removed for maintenance. Four supports per pack, one at each end of the shaft. They pair with LM8UU, LM10UU, LM12UU, and LM16UU bushings on 8mm, 10mm, 12mm, and 16mm shafts.

The 608 bearings are 8mm bore x 22mm outside diameter x 7mm wide, pre-lubricated — 608ZZ with metal double shields, or 608RS with rubber seals for dust-proof running. The flanged bearings — F623zz 3x10x4mm, F624zz 4x13x5mm, F625zz 5x16x5mm, or F626zz 6x19x6mm — hold themselves in place in the housing by the flange, so no separate retaining clip is needed.

Rebuild method

Strip the axis down to the bare shafts. Clean the shafts and check them for wear — a grooved shaft eats new bushings fast, so replace it if you can feel a ridge. Fit the new bushings and slide them by hand: smooth, no catching, no play. Bolt the shaft supports down with the shaft in place so the alignment is set by the shaft itself, not by eye. Spin every idler bearing by hand; a gritty one gets replaced. Reassemble, then run the axis end to end by hand before you power it up.

Tips

Do not over-tighten the shaft supports — you will bow the shaft. If you print new brackets, the M3 heat-set inserts (M3 x 5.7 x 4.6mm, knurled brass) give you a real thread in PLA, ABS, or PETG. Keep a few spare 608s on hand; they are the bearing that wears out everywhere.

All parts in this guide ship from NY, USA. See the full list of guides on the Drone Guides page.