Proper lubrication is the single most critical factor determining the running precision and lifespan of linear motion components. For the LM20UUOP open-type linear bearing, incorrect lubrication-either under-greasing or over-greasing-can lead to ball skid, increased friction, or seal displacement.
As a leading linear bearing manufacturer since 2007, Zhejiang Siqiang Bearing Manufacture Co., Ltd. (SQ) delivers thousands of high-precision LM20UUOP bearings globally. In this technical guide, we outline the exact lubrication volumes, grease selection criteria, and maintenance intervals for the 20mm open-type series.
Understanding the LM20UUOP Structure and Lubrication Challenge
The LM20UUOP is an Open Type linear bearing designed for a 20mm shaft supported along its entire length by a rail support. It features a cutout sector (usually 50 to 60 degrees) to clear the shaft support rails.
Because of this open structure, the internal ball circuits are partially exposed to the environment. This means:
Lubricant escapes more easily than in closed-type (LM20UU) bearings.
Dust and contaminants can enter the bearing track more readily.
Controlling the precise initial filling volume is crucial to prevent messy leakage while ensuring full ball track coating.
Recommended Lubrication Amount for LM20UUOP
Linear bearings do not require their entire internal housing to be packed 100% full of grease. Over-packing causes churn, which increases operating temperatures and creates parasitic drag.
1. Initial Grease Fill Volume (Factory Guideline)
The industry standard for high-precision linear motion is to fill 30% to 40% of the free internal space of the bearing with grease.
For an SQ manufactured LM20UUOP (Dimension: 20mm Inner Diameter, 32mm Outer Diameter, 42mm Length), the internal free volume is relatively small.
The recommended initial grease weight is approximately 0.3 to 0.45 grams per bearing.
Ensure that all 5 rows of steel balls inside the plastic retainer are evenly coated.
2. Oil Lubrication Flow Rate
If your system utilizes a centralized automated oil lubrication system instead of manual grease:
A replenishment flow rate of 0.1 to 0.3 ml/hour per bearing is highly recommended for standard industrial velocities (under 1 meter per second).
Choosing the Right Lubricant: Grease vs. Oil
| Lubricant Type | Recommended Application Scenario | SQ Expert Recommendation |
| Lithium Soap-Based Grease (NLGI No.2) | General industrial automation, medium loads, high-stability demands. | Top Pick. Stays within the open retainer structure longer and resists being thrown off by linear strokes. |
| Low-Viscosity Synthetic Oil (ISO VG 32-68) | High-speed pick-and-place, cleanroom environments, low-friction setups. | Best used with an automated continuous oil mist or drip feed system due to the open slot of the LM20UUOP. |
Warning: Avoid using greases with solid additives like MoS2 (Molybdenum Disulfide) or graphite, as they can cause the precision steel balls to skid and lock up within the retainer circuits.
Maintenance and Re-lubrication Intervals
Because the LM20UUOP operates on open support rails, the lubrication intervals depend heavily on travel distance and environment:
Standard Clean Environments: Re-lubricate every 6 months or after 100 kilometers of cumulative travel distance.
High-Dust/Woodworking/CNC Environments: Re-lubricate every 1 to 3 months. The rails must be wiped clean prior to re-greasing to prevent the creation of an abrasive grinding paste.
How to Properly Apply Grease to LM20UUOP
Clean First: If replacing old lubricant, flush the bearing with an industrial degreaser to remove all aged oil residues and trapped particles. Dry completely.
Coat the Ball Circuits: Use a fine-tip syringe nozzle to inject the grease directly into the ball paths inside the sleeve.
Distribute Manually: Slide the bearing back and forth along a 20mm precision shaft manually several times to allow the balls to distribute the grease evenly across all tracks. Wipe off any excess grease that escapes from the open sector or end seals.
Premium Linear Solutions from SQ Factory
Zhejiang Siqiang Bearing (SQ) manufactures heavy-duty LM20UUOP bearings utilizing advanced heat-treatment and precision grinding techniques to guarantee superior smooth motion. Operating across our 19,800-square-meter facility, we provide high-volume OEM manufacturing, custom surface treatments (like chrome or nickel plating), and reliable delivery worldwide.
For volume inquiries or detailed technical datasheets regarding our linear motion bearing lineup, contact our engineering sales desk today.
