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When your CNC router, 3D printer, or linear actuator demands consistent, low-friction travel, a mismatched or worn bearing becomes the weakest link in your build. These open-type LMxUU-OP linear bearings are engineered for makers, machine builders, and automation engineers who need reliable linear motion without the bulk of a closed-type housing.
Each bearing features a steel outer shell with precision-ground ball retainer and recirculating steel balls, available in ten shaft-diameter sizes ranging from 10 mm (LM10UU-OP) up to 60 mm (LM60UU-OP). The open-type (OP) slot design allows the bearing to be mounted on shafts that pass through a support bracket, reducing overall assembly height. Outer diameters span 19 mm to 90 mm; body lengths span 29 mm to 110 mm (approximately 0.75 in to 4.33 in).
Typical applications include CNC gantry axes and router Z-carriages requiring smooth linear bearing for optical shafts, RepRap and cartesian 3D printer X/Y rod systems, pick-and-place robotic arm linear slides, and DIY laser cutter bed travel assemblies — all scenarios where an open linear bearing for CNC motion control delivers measurable positioning repeatability.
The longitudinal open slot (OP) allows the bearing to clear mounting brackets and reduces assembly height — ideal for compact carriage designs where a closed bearing won't fit.
Multiple rows of recirculating steel balls distribute load evenly, delivering smooth, low-friction travel and consistent positioning accuracy across the full stroke length.
Ten shaft-diameter options from LM10UU-OP to LM60UU-OP cover the most common optical shaft sizes used in CNC, 3D printing, and industrial linear motion systems.
Hardened steel outer race and precision ball retainer resist deformation under radial load. Rubber end seals on each side retain grease and block contamination from chips and dust.
Dimensional tolerances follow standard LM-OP series specifications, making these a direct drop-in replacement for worn bearings in existing CNC and automation equipment without re-machining housings.
Order 1 pc for a single-axis test or 2 pcs to equip both sides of a gantry carriage in one purchase — select your packing quantity above.
| Bearing Series | LMxUU-OP (Open Type) |
|---|---|
| Available Types | LM10UU-OP, LM12UU-OP, LM16UU-OP, LM20UU-OP, LM25UU-OP, LM30UU-OP, LM35UU-OP, LM40UU-OP, LM50UU-OP, LM60UU-OP |
| Shaft Diameter (ID) | 10 / 12 / 16 / 20 / 25 / 30 / 35 / 40 / 50 / 60 mm |
| Outer Diameter (OD) | 19 / 21 / 28 / 32 / 40 / 45 / 52 / 60 / 80 / 90 mm |
| Body Length | 29 / 30 / 37 / 42 / 59 / 64 / 70 / 80 / 100 / 110 mm |
| Bearing Type | Open-type recirculating ball linear bearing |
| Material | Hardened steel outer race, steel ball retainer, rubber end seals |
| Shaft Tolerance Fit | h6 / h7 hardened optical shaft recommended |
| Lubrication | Pre-greased; re-lubricate with lithium grease as needed |
| Packing Quantity | 1 pc or 2 pcs (select variant) |
| Weight | See variant options |
Match the bearing's inner diameter (ID) to your shaft diameter exactly. For example, if your optical shaft is 12 mm in diameter, select the LM12UU-OP (12×21×30 mm). Using a bearing with a larger ID than your shaft will cause slop and positioning errors.
A standard LMxUU bearing has a fully enclosed cylindrical shell. The open-type (OP) variant has a longitudinal slot cut along the outer shell, allowing the bearing to be clamped into a split housing or to clear a mounting bracket. This reduces assembly height and makes it easier to install on shafts that are already fixed in place.
These bearings are designed for use with hardened and ground optical shafts (surface hardness HRC 58–64, h6 or h7 diameter tolerance). Induction-hardened shafts meeting these tolerances are compatible. Soft or un-hardened shafts will wear prematurely under the ball contact stress.
Dynamic load capacity varies by size — smaller sizes such as LM10UU-OP are rated for lighter carriage loads (typically 5–15 kgf dynamic), while larger sizes like LM40UU-OP and above handle significantly higher loads. For exact load ratings, refer to the standard LM-OP series datasheet for your chosen size, or contact us to confirm suitability for your application.
The bearings are pre-greased at the factory. For most light-duty CNC and 3D printer applications, no additional lubrication is needed before first use. For heavier-duty or high-cycle applications, apply a small amount of lithium-based grease through the open slot before installation and re-lubricate periodically.
For most linear axes, two bearings per shaft are recommended to prevent the carriage from rocking (moment load). A single bearing is sufficient only for very short travel distances or when the carriage is constrained by a second parallel shaft. Select the 2-pc packing quantity to equip both sides of a carriage in one order.
Yes. These bearings follow standard LM-OP series dimensional specifications (inner diameter, outer diameter, and body length), making them a direct drop-in replacement for worn or damaged bearings in CNC routers, 3D printers, laser cutters, and other equipment that uses the LMxUU-OP standard — no housing re-machining required.
