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When your 3D printer carriage wobbles or your CNC axis develops play, the culprit is almost always a worn or undersized linear bearing. Engineers, makers, and automation builders who demand repeatable, low-friction linear motion need a flanged bushing that mounts securely, runs quietly, and holds tolerance across thousands of cycles. These flanged linear ball bearings are engineered for exactly that — delivering smooth, precise travel on hardened steel shafts in demanding motion-control applications.
Each bearing features a steel outer shell with a precision-ground ball-retainer cage and a flanged mounting collar for positive, bolt-down installation. Available in three series — LMF (round flange), LMK (square flange), and LMH (square flange, compact) — and in both Standard (UU) and Lengthened (LUU) body styles. Bore diameters range from 6 mm (0.24 in) to 80 mm (3.15 in); outer diameters from 12 mm (0.47 in) to 120 mm (4.72 in); body lengths from 19 mm (0.75 in) up to 209 mm (8.23 in) in the lengthened variants.
Typical use cases include: X/Y/Z axis carriages on FDM 3D printers and laser engravers requiring low-backlash linear ball bearing for 3D printer smooth rod; CNC router gantry slides and plasma table linear motion systems; industrial pick-and-place automation and conveyor guide rails where a flanged linear bushing with bolt-down flange simplifies alignment; and robotics joint linkages needing compact LMH flanged bearing for tight-clearance assemblies.
Round (LMF), square (LMK), and compact square (LMH) flange styles allow direct bolt-down installation into housings or plates — no press-fit housing required, reducing assembly time and simplifying replacement.
Covers the most common shaft diameters used in desktop 3D printers (6–20 mm), CNC routers (12–40 mm), and light industrial automation (up to 80 mm), so you can source all axes from a single product family.
Standard (UU) bodies suit space-constrained builds; Lengthened (LUU) bodies provide a longer ball-contact zone for higher radial load capacity and improved moment-load resistance on cantilevered carriages.
Recirculating ball tracks distribute load evenly around the shaft, minimizing wear and maintaining consistent running clearance over the bearing's service life — critical for dimensional accuracy in CNC and printing applications.
Double-lip rubber seals on both ends retain grease and exclude dust and swarf — keeping the ball tracks lubricated and clean in workshop environments without frequent maintenance intervals.
Outer diameter, flange diameter, flange thickness, and bolt-circle dimensions follow standard LM series interchangeable geometry, making these a direct drop-in replacement for worn bearings in existing machines without redesign.
| Series | LMF (round flange), LMK (square flange), LMH (compact square flange) |
|---|---|
| Body Style | Standard (UU) / Lengthened (LUU) |
| Bore Diameter Range | 6 mm – 80 mm (0.24 in – 3.15 in) |
| Outer Diameter Range | 12 mm – 120 mm (0.47 in – 4.72 in) |
| Body Length Range (Standard) | 19 mm – 140 mm (0.75 in – 5.51 in) |
| Body Length Range (Lengthened) | 35 mm – 209 mm (1.38 in – 8.23 in) |
| Material — Outer Shell | Steel |
| Material — Ball Retainer | See variant options |
| Seals | Double-lip rubber seals (UU / LUU) |
| Shaft Tolerance (Recommended) | h7 |
| Lubrication | Grease-packed (factory pre-lubricated) |
| Flange Mounting | Bolt-down (flange bolt-circle dimensions vary by size — see variant options) |
| Radial Load Capacity | See variant options |
| Compatible Shaft Types | Hardened, ground linear shafts |
All three series share the same bore, outer diameter, and body length for a given size code — the difference is the flange shape. LMF has a round flange with evenly spaced bolt holes, ideal for circular housings or when you need to rotate the bearing for alignment. LMK has a square flange with four corner bolt holes, making it easy to mount directly to flat plates or extrusion profiles. LMH is a compact square-flange variant with a shorter flange-to-body ratio, suited for tight-clearance assemblies. Choose based on your housing geometry and available bolt pattern.
The Standard (UU) body is shorter and fits most space-constrained 3D printer and CNC carriage designs. The Lengthened (LUU) body has a longer ball-contact zone — typically 1.5–2× the standard length — which increases radial load capacity and improves resistance to moment loads (tilting forces). If your carriage is cantilevered or carries significant side loads, the LUU type is the better choice. Both types use the same shaft diameter and outer diameter, so they are interchangeable in terms of bore and OD fit.
Match the bearing bore exactly to your shaft diameter — for example, an LMF8UU requires an 8 mm shaft. For best performance and minimal play, use a hardened, ground linear shaft with an h7 diameter tolerance. Soft or unground shafts will wear the ball tracks prematurely and increase running clearance over time. Shafts with an f7 or g6 tolerance are also acceptable for light-duty applications.
The standard steel outer shell and balls offer moderate corrosion resistance when kept lubricated and sealed. The double-lip rubber seals help exclude moisture and contaminants. For consistently humid, wet, or mildly corrosive environments, we recommend applying a light coat of corrosion-inhibiting grease during installation and re-lubricating periodically. For highly corrosive environments, consider stainless-steel shaft and housing combinations alongside these bearings.
Yes. These bearings follow standard LM-series interchangeable geometry — the bore, outer diameter, body length, flange diameter, flange thickness, and bolt-circle dimensions match the industry-standard LMF/LMK/LMH dimensional specifications. As long as you select the same model code (e.g., LMF12UU for LMF12UU), they will drop in without modification to your housing or shaft.
Check your machine's documentation or measure the existing bearing: note the shaft diameter (bore), the outer diameter of the bearing body, and the body length. Match these three dimensions to the size table in the variant selector — the option label shows Bore × O.D × Length in mm. Common 3D printer sizes are 6 mm, 8 mm, 10 mm, and 12 mm bore; common CNC router sizes range from 12 mm to 30 mm bore. If you are unsure, contact us with your machine model and we can confirm the correct size.
Yes, each bearing is factory pre-lubricated with grease before the seals are installed. For most 3D printing and light CNC use, no additional lubrication is needed at installation. For heavier-duty or high-cycle applications, apply a small amount of lithium-based or NLGI #2 grease to the shaft before assembly. Re-lubricate every 6–12 months or when you notice increased running noise or resistance.
