Linear Bearings LMK/LMF/LMH Series

These three series are important variants of the standard LM (Linear Motion) bearings, primarily differing in the shape and mounting method of the outer ring to meet diverse mechanical design requirements.
Core Commonality:
Their internal structure (cage, steel balls, seals) is essentially identical to that of standard LM/UU bearings of the same size, offering the same inner diameter, precision, and load capacity. The differences lie entirely in the housing (outer ring).

Introduction

I. LMK: Square Flange Linear Bearings

Positioning: Square flange-mounted linear bearings. They integrate the bearing body and a square mounting flange into a single unit.

Structural Features:

Standard LM Core: The central part is a complete LM bearing.
Integrated Square Flange: The outer ring is surrounded by a square flange plate, typically with four symmetrical mounting holes.

Core Advantages and Applications:

Extremely Easy Installation: No additional SHF or SK support blocks are required. The bearing can be directly fixed to a machine frame panel or plate via the screw holes on the flange.
Space and Component Savings: Eliminates the need for separate support blocks, resulting in a more compact structure, fewer parts, and a simplified BOM (Bill of Materials).
High Rigidity Connection: The square flange provides a stable mounting surface with strong torsional resistance.

Typical Applications: Ideal for scenarios requiring direct installation on flat or thick plates, such as custom-made small equipment, experimental benches, space-constrained mechanisms, or designs aiming for simplicity. A popular choice for DIY and light industrial applications.

II. LMF: Round Flange Linear Bearings

Positioning: Round flange-mounted linear bearings.

Structural Features:

Standard LM Core: Same as LMK.
Integrated Round Flange: The outer ring is surrounded by a circular flange plate, typically with three or four evenly distributed mounting holes around its circumference.

Core Advantages and Applications:

Flexible Installation, Saves Radial Space: The round flange allows 360° rotational adjustment after mounting for easier alignment. Its outer profile is generally more compact than that of a square flange, offering advantages in radially constrained spaces.
Aesthetic and Streamlined Design: Provides a smoother appearance.
Typical Applications: Often used in scenarios requiring flexible directional adjustment or where mounting space is circular, such as certain lightweight robotic joints or linear guides in rotational transition sections.

III . LMH: Internal Threaded/Threaded Stud Linear Bearings

Positioning: Threaded stud/bushing-type linear bearings. This is a unique and highly useful design.

Structural Features:

Standard LM Core: Also features a linear bearing core.
Threaded Housing: The outer surface is not a smooth cylinder but is machined with standard external threads.

Core Advantages and Applications:

Threaded Installation, No Support Blocks Required: Can be directly screwed into a pre-tapped mounting hole or secured with nuts on both sides of a panel.
Axial Position Fine Adjustment: The bearing can be rotated to precisely fine-tune its depth position, which is particularly useful for dual-axis systems requiring precise alignment.
Facilitates Rear Installation: Allows installation and tightening from the rear when front panel space is limited.

Typical Applications: Scenarios demanding high installation precision and adjustability, such as precision optical adjustment mounts, dual-guide systems requiring parallelism fine-tuning, or thin-walled structures where flanges or support blocks cannot be used.

IV. Comparison Table: LMK vs. LMF vs. LMH vs. Standard LM + Support Block

Characteristic	LMK (Square Flange)	LMF (Round Flange)	LMH (Threaded Stud)	Standard LM + SHF/SK Support Block
Mounting Method	Direct screw mounting via flange	Direct screw mounting via flange	Threaded screwing into place	Bearing first inserted into support block, then block is fixed
Core Advantage	Simple installation, fewer parts, high rigidity.	Flexible mounting, saves radial space.	Position is finely adjustable, allows rear mounting, flexible.	Most versatile and standard. Support blocks can be split-type (SHF), offering excellent maintenance convenience.
Mounting Complexity	Simplest (one-step).	Simple.	Moderate (requires ensuring threaded fit).	Most complex (two-step: insert bearing into block, then mount block).
Adjustability	Non-adjustable after fixing.	Angle can be rotated before fixing.	Axial position can be precisely fine-tuned.	Achieved by adjusting the support block position, but it is more troublesome.
Moment Resistance	Strong (square flange resists torsion).	Moderate.	Weak (relies on threads for torsion resistance).	Strongest (support block has large flange, good force distribution).
Maintenance Convenience	Poor (requires complete disassembly).	Poor.	Moderate (can be unscrewed).	Best (SHF type allows opening the cover to replace the bearing without shaft removal).
Application Scenario	Direct mounting on flat plates, sufficient space, seeking simplicity.	Compact space, requires angle adjustment.	Requires fine-tuning, thin-wall mounting, special structures.	Most industrial equipment, prioritizing reliability and maintainability.
Cost Consideration	High unit cost, but saves on support block.	High unit cost, but saves on support block.	High unit cost.	LM bearing cost is low, but total cost with support block may be comparable or slightly lower.

V . Selection Guidelines and Key Points

Prioritize Standard LM + SHF Support Blocks: For serious industrial designs, projects requiring maintenance, or designs not yet finalized, this is the most recommended, flexible, and reliable solution. The separable design of SHF is a significant advantage.

When to Choose LMK/LMF:

Mass production with finalized designs aiming to reduce part count and assembly steps.
Closed products (e.g., consumer electronics) with sufficient space and no future maintenance needs.
DIY or prototyping requiring quick assembly.

When to Choose LMH:

When precise axial fine-tuning is essential.
Mounting on thin plates or profiles without sufficient thickness for support blocks.
When front access is impossible, and rear installation is necessary.

General Considerations:

Regardless of the model, always pair with high-precision hard-chrome linear shafts.

Ensure loads pass primarily through the bearing center to avoid overturning moments.

Pay attention to lubrication; flange types (LMK/LMF) may be less convenient to lubricate than standard LM bearings with grease fittings.

Summary:

The LMK, LMF, and LMH series are intelligent extensions of standard linear bearing applications. By modifying the outer ring form, they integrate bearing functionality with mounting solutions, offering optimized options for specific scenarios.

LMK/LMF are "designed for quick installation," trading integration for assembly efficiency.

LMH is "designed for flexible adjustment and special mounting," offering unparalleled tuning flexibility through threaded connections.

However, this integration sacrifices the maintainability and design flexibility of the standard LM + separable support block (SHF) solution. Therefore, during selection, it is crucial to prioritize the entire process—installation, maintenance, and adjustment—rather than focusing solely on individual component characteristics. For most industrial applications, the modular standard solution remains the most robust choice in the long run.