KH vs LM Linear Ball Bearings: Dimensions, Design and Selection
KH and LM linear ball bearings can both guide linear movement along a round shaft, but they are not simply two names for the same bearing. The main difference is the bearing format and the space it requires inside the machine. KH bearings use a compact drawn-cup construction, while standard LM bearings use a conventional cylindrical linear-bushing format.
For an OEM designer, distributor or maintenance buyer, that difference affects the housing, outside diameter, bearing length, mounting method and replacement decision. A matching shaft diameter alone does not mean that a KH and LM bearing can be substituted for each other.
KH vs LM Linear Bearings at a Glance
| Selection Factor | KH Series | LM Series |
|---|---|---|
| Basic format | Compact drawn-cup linear bearing | Conventional cylindrical linear bushing |
| Shaft type | Round shaft | Round shaft |
| Radial installation space | Designed around a compact radial envelope | Typically uses the conventional LM cylindrical envelope |
| Housing consideration | Housing must suit the KH outside diameter, length and mounting arrangement | Housing must suit the selected LM model and configuration |
| Sealing | Depends on designation; the DISLAB KH..PP range uses end sealing/wiping elements | Depends on the selected LM model and manufacturer |
| Replacement decision | Check full designation, dimensions, load ratings, housing and operating requirements before substitution | |
This comparison describes the bearing formats rather than declaring one series superior. Actual product specifications vary by model and manufacturer.
What Is a KH Series Linear Ball Bearing?
A KH bearing is a compact linear ball bearing with a drawn-cup outer sleeve and recirculating balls. It runs along a round shaft and is particularly useful when the machine designer has limited radial space around that shaft.
The compact outer envelope is the main reason to consider KH. It can allow a machine layout to use a smaller bearing outside diameter than a bulkier bearing arrangement, provided the housing, shaft and operating conditions are compatible with the selected model.
DISLAB Precision’s current KH..PP range covers shaft diameters from 6 to 50 mm. Buyers who need model dimensions, basic load ratings and weights should use the KH Series compact drawn cup linear bearing product page rather than relying on a generic comparison chart.
What Is an LM Series Linear Ball Bearing?
Standard LM bearings use a conventional cylindrical linear-bushing format for motion along round shafts. The LM family is widely represented in industrial linear-motion systems and is available in several configurations, including standard cylindrical, long, flanged, open and adjustable designs depending on the product family.
This broader range of formats can make LM useful where a machine or existing housing has already been designed around a conventional linear bushing. The important point is that “LM” describes a product family rather than one universal bearing geometry.
For available configurations and sourcing information, see the LM Series linear ball bearing product page.
The Main Difference: Installation Envelope
The most useful first comparison is not the number of balls or the appearance of the bearing. It is the space available around the shaft.
KH is designed as a compact drawn-cup format with a small radial envelope. That can matter in compact automation equipment, measuring mechanisms, packaging systems or other assemblies where the distance between the shaft and surrounding machine components is limited.
A conventional LM bearing normally requires the housing to accommodate its own cylindrical outside diameter and length. If the machine is already designed around an LM housing, changing to KH is not automatically beneficial because the surrounding components may also need to change.
Housing and Mounting Requirements Are Different
The bearing is only one part of a linear-motion assembly. The shaft, housing, alignment, retention method and lubrication arrangement all affect whether a particular bearing format can be used.
A KH bearing should be evaluated against the housing bore and support arrangement intended for the compact drawn-cup design. Installation force, housing condition and alignment must be controlled so the bearing sleeve is not damaged or distorted.
LM bearings also require a housing compatible with the selected model. Standard cylindrical, flanged, open and adjustable LM variants do not all use the same mounting arrangement. An existing LM installation therefore should be identified by its complete designation and housing configuration before a replacement is selected.
Do KH and LM Bearings with the Same Shaft Diameter Interchange?
Not necessarily.
Two bearings may both fit a 20 mm shaft, for example, while having different outside diameters, lengths, housing requirements, sealing arrangements and basic load ratings. Manufacturer-specific internal designs may also differ.
For maintenance replacement, compare at least the full bearing designation, shaft diameter, outside diameter, bearing length, housing drawing, dynamic load rating, static load rating and sealing configuration. If the original machine drawing or bearing datasheet is available, include it with the RFQ.
A visual match or matching bore diameter is not sufficient evidence of interchangeability.
How Should Load Ratings Be Compared?
Dynamic and static load ratings are important selection inputs, but they should be compared using the actual datasheets for the models being considered. A product-family name alone does not establish load capacity.
Dynamic load rating and static load rating also describe different loading conditions. Neither value should be treated as a universal allowable machine load without considering bearing arrangement, load direction, duty cycle, shock, alignment and other operating conditions.
This is one reason the KH product page lists the verified ratings for DISLAB’s available KH..PP range rather than assuming that every manufacturer’s KH bearing has identical values.
What About Seals and Contamination?
Sealing requirements should be considered separately from bearing size. The KH..PP products represented on the DISLAB KH page include sealing or wiping elements at both ends, but this does not make the bearing suitable for every dusty, wet or chemically exposed environment.
LM bearing sealing options vary with model and manufacturer. When requesting a quote, describe the operating environment and identify whether contamination, moisture, cleaning processes or lubricant retention are important to the application.
For either format, special environmental suitability should be confirmed rather than assumed from the product-family name.
When Does the KH Format Make Sense?
KH is worth evaluating when the machine has limited radial installation space around a round shaft and the compact drawn-cup geometry fits the intended housing. It may also be relevant when an existing machine already uses a KH designation and the buyer wants a replacement in the same general format.
Typical purchasing situations include compact automation mechanisms, linear stages, assembly equipment, packaging machinery, measuring systems and other round-shaft motion assemblies where the housing envelope is constrained.
The decision still requires checking the selected model’s dimensions, load ratings, shaft condition, housing and operating environment.
When Does the LM Format Make Sense?
LM is worth evaluating when the machine is designed around a conventional cylindrical linear bushing or when the required mounting arrangement is available within the LM product family.
For example, an OEM may already have a housing based on a standard cylindrical LM bearing, while another application may require a flanged, open, adjustable or long-style configuration. In those cases, changing to a compact KH format may provide no practical benefit unless the machine itself is being redesigned.
The correct choice is the format that matches the complete mechanical arrangement and operating requirements.
KH or LM? A Practical Selection Process
- Identify the shaft diameter. Confirm the actual shaft size rather than estimating from the old bearing.
- Measure the available housing space. Check the maximum outside diameter, available bearing length and surrounding components.
- Identify the current bearing format. Record the complete KH, LM or other manufacturer designation if this is a replacement.
- Compare actual load ratings. Use the datasheets for the specific candidate models rather than generic family assumptions.
- Review mounting and retention. Confirm how the bearing is supported and retained in the housing.
- Describe the environment. Include contamination, moisture, lubrication and cleaning requirements.
- Check operating conditions. Provide motion cycle, load conditions and any known speed or temperature requirements for product-specific review.
- Send the complete RFQ. Include quantity, destination country and any drawing or reference specification available.
Which One Should You Choose?
Choose by machine geometry and verified operating requirements, not by a general assumption that KH or LM is the “better” bearing.
If radial installation space is the main constraint, start by evaluating the KH compact format. If the assembly is already designed around a conventional cylindrical linear bushing or requires an LM-family mounting configuration, start with the LM series. For replacement work, preserve the original housing and shaft requirements unless the machine is intentionally being redesigned.
Compare DISLAB Precision Linear Bearing Options
Use the two product pages below for commercial specifications and quotation requests:
- KH Series Compact Drawn Cup Linear Ball Bearings — KH..PP models, dimensions and verified load ratings.
- LM Series Linear Ball Bearings — conventional LM-family product options and sourcing information.
If you are not sure which format matches the machine, send the shaft size, available housing dimensions, current model number and expected operating conditions with your inquiry.