The INA KS20-PP is a heavy-duty self-aligning linear ball bearing from the Schaeffler INA brand. Part of the KS series—featuring heavy-load capacity, sealed design, and clearance-adjustable seals—it is designed for high-precision linear motion on 50 mm-diameter plain shafts, delivering outstanding performance in self-alignment, high rigidity, low friction, and long service life.

The INA KS50-PP is a heavy-duty self-aligning linear ball bearing from the Schaeffler INA brand. Part of the KS series—featuring heavy-load capacity, sealed design, and clearance-adjustable seals—it is designed for high-precision linear motion on 50 mm-diameter plain shafts, delivering outstanding performance in self-alignment, high rigidity, low friction, and long service life.

II. Core Dimensions and Performance Parameters

1. Critical dimensions (mm)
Inner diameter (Fw): 50 (compatible with φ50 mm optical shaft)
Outer diameter (D): 75
Length (L): 100
Weight: ≈0.59 kg

2. Rated Load (N)
Basic dynamic load rating C: 12,300 (minimum) / 15,100 (maximum)
Basic static load rating C₀: 9,700 (minimum) / 13,900 (maximum)

3. Structure and Motion Parameters
Ball row count: 8 rows (evenly distributed around the circumference for uniform load bearing)
Self-alignment capability: ±40 arcminutes (≈±0.67°), capable of compensating for shaft misalignment errors.
Coefficient of friction: 0.001–0.003 (rolling friction, low noise, no stick-slip)
Maximum speed: 5 m/s; maximum acceleration: 100 m/s²
Sealing: Double-sided clearance seal (standard); optional PP lip seal (dust- and splash-proof, IP54)
Temperature range: -20°C to +80°C (standard sealing)
III. Detailed Structural Analysis
1. Four Core Components
Steel housing: made of high-carbon chromium steel, through-hardened and quenched (HRC 60 ± 2), offering high rigidity and excellent resistance to deformation; features a sealed, circumferentially closed design, suitable for circumferential load-bearing applications.
Self-aligning rolling-element units (segmented type): a total of 8 sets, capable of radial micro-oscillation and providing automatic self-alignment within ±40′; each set comprises an upper cage, a load-bearing plate, steel balls, and a lower cage. The steel balls circulate on the quenched and precision-ground load-bearing plate, achieving four-point contact loading and high stiffness.
Steel Balls: G10-grade, high-precision chrome steel balls with a diameter of approximately 8 mm, arranged in eight evenly spaced rows around the circumference, offering strong load-carrying capacity and smooth operation.

Seals: Standard configuration is a double-sided clearance seal (effectively preventing the ingress of large particulate dust); optional PP lip seal (contact-type, offering dust-proof, oil-proof, and splash-water-proof performance, suitable for harsh operating conditions).

2. Operating Principle (Self-Aligning + Recirculating Rolling)

Self-aligning compensation: Eight sets of rolling-element units float independently in the radial direction, automatically compensating for misalignment between the shaft and the bearing housing (≤±40′), thereby eliminating edge stresses, reducing wear, and extending service life.

Reduced cyclic rolling friction: The steel balls circulate between the bearing plate and the optical axis, converting sliding friction (μ ≈ 0.1) into rolling friction (μ ≈ 0.001), thereby achieving low friction, low noise, high-speed stability, and elimination of stick-slip phenomena.

Circumferential Load-Bearing Rigidity: Eight rows of steel balls are evenly distributed around the circumference, providing excellent radial and axial stiffness. The bearing can withstand radial loads, small axial loads, and overturning moments, making it suitable for heavy-load applications and scenarios with high rigidity requirements.

IV. Core Advantages (Comparison with Standard Linear Bearings)

Outstanding self-alignment performance: ±40′ automatic alignment effectively compensates for installation errors, reduces machining and assembly complexity, prevents jamming, and minimizes wear.

High-load, high-rigidity design: 8-row ball bearing with quenched bearing housing, rated dynamic load of 12.3 kN—more than 30% higher than that of standard linear bearings of the same size—making it ideal for heavy-load and impact applications.

Low friction and high-speed, smooth operation: rolling friction combined with precision-ground raceways results in low noise (≤50 dB), no stick-slip phenomenon, and a maximum operating speed of up to 5 m/s, making it ideal for precision positioning and high-speed conveying.

Long service life and maintenance-free operation: Constructed with high-quality materials and featuring a self-aligning design, the product boasts a service life of ≥10,000 hours; standard initial lubrication and gap-sealed dustproof design ensure long-term, maintenance-free operation.

Compact structure and easy installation: outer dimensions φ75×100 mm; can be directly press-fitted into the bearing housing (H7 fit), offering convenient installation and excellent interchangeability.

V. Typical Application Scenarios

1. Automation equipment (core features: high precision, high speed, low friction)

3C equipment: precision linear motion axes for CNC machining centers, laser cutting machines, and pick-and-place machines, featuring high-speed positioning and exceptional repeat accuracy.

Automated production lines: heavy-duty linear guides for conveyor systems, transplanting machines, and lifting platforms; ensuring smooth conveyance, low noise, and long service life.

2. Textile machinery (key features: high speed, low noise, dust-proof)
Knitting circular machines, flat-seam sewing machines, and embroidery machines: equipped with high-speed rotary or linear guide rails; resistant to fiber dust; low noise; service life of ≥8,000 hours.

3. Packaging and Food Machinery (Core Requirements: Cleanliness, Low Friction, Corrosion Resistance)
Filling/sealing machines, labeling machines, and rotary conveyors: feature stainless steel shafts with sealed bearings; suitable for high-temperature cleaning and humid environments; maintenance-free and free from oil contamination.

4. Medical and Optical Equipment (Core Requirements: High Precision, Low Friction, Low Noise)
Medical imaging equipment (CT/X-ray machines), precision instruments, and optical platforms: low friction, low noise, and high stability ensure clear imaging and precise positioning.

5. General-Purpose Machinery and Tooling (Core Features: Heavy-Load Capacity, Self-Aligning Capability, and Easy Installation)
Hydraulic equipment, pneumatic pumps, fire pumps, gear hobbing machines, and tooling fixtures: Featuring heavy-duty guiding and self-aligning compensation designs to accommodate installation errors, reduce wear, and enhance reliability.

VI. Installation and Selection Considerations
1. Installation Requirements
Compatible optical axis: φ50 mm, quenched to HRC 60±2 and precision-ground to Ra ≤ 0.4 μm. Insufficient hardness will shorten bearing life.

Bearing housing fit: The outer diameter of the bearing housing is 75 mm; an H7 hole fit is recommended, with a press-fit installation to ensure coaxiality.

Lubrication: Standard initial lubrication with lithium-based grease; when the operating temperature exceeds 60°C or under high-speed operating conditions, the grease should be replenished regularly (every 1,000 hours). 1. Seal Selection: For ordinary dusty environments, use standard clearance seals; for humid, heavily dusty, or oil-mist-splashing environments, select KS50-PP lip seals.

2. Key selection parameters:

Shaft diameter: Must be φ50 mm (compatible with KS50).

Load ratings: radial load ≤ 12.3 kN; axial load ≤ 2 kN; overturning moment ≤ 50 Nm.

Accuracy: Repeatability of motion positioning ≤ ±0.01 mm (suitable for precision equipment).

Environmental factors—temperature, dust, and humidity—should be taken into account when selecting the appropriate seal type and material.

Speed/Acceleration: ≤5 m/s, ≤100 m/s² (suitable for high-speed operating conditions).

VII. Model Comparison and Replacement

Standard model: KS50 (closed-type, clearance seal, heavy-duty)

Seal Upgrade: KS50-PP (Double-Lip Seal, Dust- and Splash-Proof)

Open-type: KSO50 (open design, compatible with support rails, easy installation and maintenance)

Abstract
The INA KS50 is a heavy-duty self-aligning linear bearing specifically designed for 50-mm optical shafts. Its core features include eight rows of self-aligning rolling elements, a quenched and hardened bearing housing, and low-friction recirculating rolling motion, delivering five key advantages: self-alignment, high load-carrying capacity and stiffness, low friction and high-speed operation, long service life, and easy installation. This product is widely used in high-precision, heavy-load linear-motion applications across industries such as automation, textiles, packaging, medical equipment, and general machinery, making it the ideal choice for heavy-load guidance of φ50-mm optical shafts.

II. Core Dimensions and Performance Parameters

1. Critical dimensions (mm)
Inner diameter (Fw): 50 (compatible with φ50 mm optical shaft)
Outer diameter (D): 75
Length (L): 100
Weight: ≈0.59 kg

2. Rated Load (N)
Basic dynamic load rating C: 12,300 (minimum) / 15,100 (maximum)
Basic static load rating C₀: 9,700 (minimum) / 13,900 (maximum)

3. Structure and Motion Parameters
Ball row count: 8 rows (evenly distributed around the circumference for uniform load bearing)
Self-alignment capability: ±40 arcminutes (≈±0.67°), capable of compensating for shaft misalignment errors.
Coefficient of friction: 0.001–0.003 (rolling friction, low noise, no stick-slip)
Maximum speed: 5 m/s; maximum acceleration: 100 m/s²
Sealing: Double-sided clearance seal (standard); optional PP lip seal (dust- and splash-proof, IP54)
Temperature range: -20°C to +80°C (standard sealing)
III. Detailed Structural Analysis
1. Four Core Components
Steel housing: made of high-carbon chromium steel, through-hardened and quenched (HRC 60 ± 2), offering high rigidity and excellent resistance to deformation; features a sealed, circumferentially closed design, suitable for circumferential load-bearing applications.
Self-aligning rolling-element units (segmented type): a total of 8 sets, capable of radial micro-oscillation and providing automatic self-alignment within ±40′; each set comprises an upper cage, a load-bearing plate, steel balls, and a lower cage. The steel balls circulate on the quenched and precision-ground load-bearing plate, achieving four-point contact loading and high stiffness.
Steel Balls: G10-grade, high-precision chrome steel balls with a diameter of approximately 8 mm, arranged in eight evenly spaced rows around the circumference, offering strong load-carrying capacity and smooth operation.

Seals: Standard configuration is a double-sided clearance seal (effectively preventing the ingress of large particulate dust); optional PP lip seal (contact-type, offering dust-proof, oil-proof, and splash-water-proof performance, suitable for harsh operating conditions).

2. Operating Principle (Self-Aligning + Recirculating Rolling)

Self-aligning compensation: Eight sets of rolling-element units float independently in the radial direction, automatically compensating for misalignment between the shaft and the bearing housing (≤±40′), thereby eliminating edge stresses, reducing wear, and extending service life.

Reduced cyclic rolling friction: The steel balls circulate between the bearing plate and the optical axis, converting sliding friction (μ ≈ 0.1) into rolling friction (μ ≈ 0.001), thereby achieving low friction, low noise, high-speed stability, and elimination of stick-slip phenomena.

Circumferential Load-Bearing Rigidity: Eight rows of steel balls are evenly distributed around the circumference, providing excellent radial and axial stiffness. The bearing can withstand radial loads, small axial loads, and overturning moments, making it suitable for heavy-load applications and scenarios with high rigidity requirements.

IV. Core Advantages (Comparison with Standard Linear Bearings)

Outstanding self-alignment performance: ±40′ automatic alignment effectively compensates for installation errors, reduces machining and assembly complexity, prevents jamming, and minimizes wear.

High-load, high-rigidity design: 8-row ball bearing with quenched bearing housing, rated dynamic load of 12.3 kN—more than 30% higher than that of standard linear bearings of the same size—making it ideal for heavy-load and impact applications.

Low friction and high-speed, smooth operation: rolling friction combined with precision-ground raceways results in low noise (≤50 dB), no stick-slip phenomenon, and a maximum operating speed of up to 5 m/s, making it ideal for precision positioning and high-speed conveying.

Long service life and maintenance-free operation: Constructed with high-quality materials and featuring a self-aligning design, the product boasts a service life of ≥10,000 hours; standard initial lubrication and gap-sealed dustproof design ensure long-term, maintenance-free operation.

Compact structure and easy installation: outer dimensions φ75×100 mm; can be directly press-fitted into the bearing housing (H7 fit), offering convenient installation and excellent interchangeability.

V. Typical Application Scenarios

1. Automation equipment (core features: high precision, high speed, low friction)

3C equipment: precision linear motion axes for CNC machining centers, laser cutting machines, and pick-and-place machines, featuring high-speed positioning and exceptional repeat accuracy.

Automated production lines: heavy-duty linear guides for conveyor systems, transplanting machines, and lifting platforms; ensuring smooth conveyance, low noise, and long service life.

2. Textile machinery (key features: high speed, low noise, dust-proof)
Knitting circular machines, flat-seam sewing machines, and embroidery machines: equipped with high-speed rotary or linear guide rails; resistant to fiber dust; low noise; service life of ≥8,000 hours.

3. Packaging and Food Machinery (Core Requirements: Cleanliness, Low Friction, Corrosion Resistance)
Filling/sealing machines, labeling machines, and rotary conveyors: feature stainless steel shafts with sealed bearings; suitable for high-temperature cleaning and humid environments; maintenance-free and free from oil contamination.

4. Medical and Optical Equipment (Core Requirements: High Precision, Low Friction, Low Noise)
Medical imaging equipment (CT/X-ray machines), precision instruments, and optical platforms: low friction, low noise, and high stability ensure clear imaging and precise positioning.

5. General-Purpose Machinery and Tooling (Core Features: Heavy-Load Capacity, Self-Aligning Capability, and Easy Installation)
Hydraulic equipment, pneumatic pumps, fire pumps, gear hobbing machines, and tooling fixtures: Featuring heavy-duty guiding and self-aligning compensation designs to accommodate installation errors, reduce wear, and enhance reliability.

VI. Installation and Selection Considerations
1. Installation Requirements
Compatible optical axis: φ50 mm, quenched to HRC 60±2 and precision-ground to Ra ≤ 0.4 μm. Insufficient hardness will shorten bearing life.

Bearing housing fit: The outer diameter of the bearing housing is 75 mm; an H7 hole fit is recommended, with a press-fit installation to ensure coaxiality.

Lubrication: Standard initial lubrication with lithium-based grease; when the operating temperature exceeds 60°C or under high-speed operating conditions, the grease should be replenished regularly (every 1,000 hours). 1. Seal Selection: For ordinary dusty environments, use standard clearance seals; for humid, heavily dusty, or oil-mist-splashing environments, select KS50-PP lip seals.

2. Key selection parameters:

Shaft diameter: Must be φ50 mm (compatible with KS50).

Load ratings: radial load ≤ 12.3 kN; axial load ≤ 2 kN; overturning moment ≤ 50 Nm.

Accuracy: Repeatability of motion positioning ≤ ±0.01 mm (suitable for precision equipment).

Environmental factors—temperature, dust, and humidity—should be taken into account when selecting the appropriate seal type and material.

Speed/Acceleration: ≤5 m/s, ≤100 m/s² (suitable for high-speed operating conditions).

VII. Model Comparison and Replacement

Standard model: KS50 (closed-type, clearance seal, heavy-duty)

Seal Upgrade: KS50-PP (Double-Lip Seal, Dust- and Splash-Proof)

Open-type: KSO50 (open design, compatible with support rails, easy installation and maintenance)

Abstract
The INA KS50 is a heavy-duty self-aligning linear bearing specifically designed for 50-mm optical shafts. Its core features include eight rows of self-aligning rolling elements, a quenched and hardened bearing housing, and low-friction recirculating rolling motion, delivering five key advantages: self-alignment, high load-carrying capacity and stiffness, low friction and high-speed operation, long service life, and easy installation. This product is widely used in high-precision, heavy-load linear-motion applications across industries such as automation, textiles, packaging, medical equipment, and general machinery, making it the ideal choice for heavy-load guidance of φ50-mm optical shafts.