Shaft-guided linear bearings
LM Linear Motion Bearings
LM linear bearings and linear ball bushings for shaft-guided low-friction linear motion in automation and packaging machinery.
LM linear bearing principle
LM linear ball bearings (linear bushings) run on hardened precision shafts with recirculating ball paths. They provide economical linear guidance for automation, packaging, medical equipment and general machinery where profile rail systems are not required.
This legacy URL is distinct from the linear motion bearings overview page at linear motion bearings, which covers broader linear engineering topics.
How an LM linear bushing works
Inside the bushing housing, recirculating balls roll between the inner raceway and the outer hardened shaft. The balls follow a closed circuit: they load on the shaft, return through the housing, and re-enter the load zone. This rolling contact replaces sliding friction with controlled rolling friction.
Load is carried primarily in the radial direction relative to the shaft. Moment capacity is limited compared with profile rail guides, so shaft support spacing and system stiffness become important design factors.
LM linear bushings and shaft linear bearings are marketed under many manufacturer naming conventions. THK linear bushings, NB (Nippon Bearing) linear bearings for shaft guidance, and INA linear ball bearings are examples commonly seen in manufacturer literature for automation and packaging machinery. Flanged linear bearing, open linear bearing, and compact linear bearing housing styles vary by supplier; verify load ratings and seals before substitution.
Selection notes
Shaft hardness
Shaft raceway hardness and surface finish strongly affect life and friction.
Support spacing
Shaft deflection limits accuracy; use adequate shaft diameter and support spacing.
Sealing
Open, sealed and adjustable variants exist across manufacturers.
LM configuration types
Flangeless (standard)
Cylindrical housing for bore-mounted installations with minimal envelope.
Round flange
Circular mounting flange for bolt-on attachment; a common flanged linear bearing layout.
Square flange
Flat flange face for four-bolt mounting and stable orientation.
Oval / cut flange
Reduced or shaped flange variants for space-limited layouts where manufacturers offer them.
Open type
Open linear bearing path for supported shaft applications or custom lubrication access.
Encased / sealed
Rubber or metal seals to retain grease and exclude contamination.
Self-aligning
Housing accommodates minor misalignment between shaft and mounting face.
Compact / miniature
Reduced outer diameter for medical, electronic, and light automation modules.
LM shaft requirements
Hardness
Shaft raceway hardness must suit rolling contact; soft shafts shorten life and increase wear.
Surface finish
Smooth, defect-free raceway finish reduces brinelling and friction spikes.
Straightness
Bowed or bent shafts create uneven loading and stick-slip motion.
Support and spacing
Unsupported shaft spans deflect under load; use adequate diameter and support blocks.
Alignment
Parallel shafts and square mounting faces prevent edge loading on the ball circuit.
Shaft diameter
Diameter sets basic load capacity and stiffness; match bushing bore to shaft nominal size.
LM selection factors
Load
Radial load and any overturning moment from cantilevered masses.
Speed
Higher speed increases heat and lubrication demand.
Stroke
End support and shaft length must cover full travel without excessive overhang.
Environment
Dust, moisture, or washdown duty may require sealed variants and corrosion-resistant shafts.
Lubrication
Grease or oil compatible with seals and duty cycle.
Sealing
Open, single-seal, or double-seal options trade contamination resistance against friction.
Alignment tolerance
Self-aligning types help where perfect parallelism is difficult to achieve.
Shaft support layout
Number and position of shaft supports define deflection and accuracy.
LM applications
Packaging machinery
Indexing, filling, and transfer modules with moderate precision; typical linear bearings for packaging machinery.
Medical and laboratory
Smooth low-friction travel in compact equipment envelopes.
General automation
Pick-and-place axes, doors, and adjustable fixtures.
Material handling
Shuttle and pusher mechanisms on supported shafts.
Printing and converting
Registration and tension control with economical shaft guidance.
Jigs and fixtures
Adjustable slides where profile rail stiffness is not required.
LM bushing vs profile rail
| Load and moment | Profile rail guides generally offer higher moment stiffness per footprint. |
|---|---|
| Alignment | LM systems tolerate simpler shaft-and-support layouts; profile rails need precise rail mounting. |
| Cost and complexity | LM on round shaft is often more economical for moderate-duty automation. |
| Precision | Machine-tool-grade profile rails suit tighter accuracy budgets than general LM bushings. |
| Maintenance | Both need clean lubrication; LM life is highly sensitive to shaft condition. |
LM maintenance
LM systems remain reliable when shaft condition, lubrication, and alignment are maintained together.
- Lubrication -- Replenish grease or oil per manufacturer guidance; dry running accelerates raceway damage.
- Contamination -- Inspect seals; wipe shafts before assembly in dusty environments.
- Shaft condition -- Scoring, corrosion, or soft spots require shaft replacement or refinishing before fitting new bushings.
- Alignment -- Re-check parallelism after machine moves or impacts that may shift supports.
- Inspection -- Listen for roughness, measure increased backlash, and replace bushings when travel becomes uneven.
Catalogue status
LM size codes (e.g. LM6 to LM80) are industry-standard designations across multiple manufacturers. Golden Bearing Company confirms supply against verified stock and manufacturer data on enquiry.
Common questions
An LM linear bearing (linear ball bushing) is a recirculating-ball unit that slides on a hardened precision shaft. It provides economical linear guidance for automation and general machinery.
Shaft raceways must be hard enough for rolling contact. Soft or unhardened shafts shorten life and increase friction. Confirm shaft specification with your bushing manufacturer.
Support spacing limits shaft deflection under load and at full stroke overhang. Increase shaft diameter or add supports when accuracy drops or bushings bind.
Sealed types retain lubricant and exclude contamination. Open types suit supported-rail applications or where external shields are provided by the machine design.
Not always. LM suits moderate radial loads and simpler layouts. High moment stiffness, machine-tool accuracy, or long heavy-duty gantries usually need profile rail guides.
LM6 to LM80 are common industry designations, but load ratings, seals, and internal geometry differ by manufacturer. Verify ratings before substitution.
Keep shafts clean and lubricated, protect seals, maintain alignment, and replace bushings when travel becomes rough or noisy.
THK, NB (Nippon Bearing), INA/Schaeffler, IKO, and SKF publish linear bushing and shaft linear bearing families in manufacturer literature. Naming such as LM linear bearing or linear ball bushing is generic; series designations, seals, and load ratings are manufacturer-specific.
No. Model-level load and speed data publish only with manufacturer verification. Send bore size, stroke, speed, and load duty for engineering quotation.
Request an Engineering Quote
Share shaft bore, speed, torque duty and ordering designation for LM Linear Motion Bearings. Golden Bearing Company supports engineering-led quotation for industrial bearings and couplings.