440C Stainless Steel Balls
Ball Bearing
High-Hardness, Wear-Resistant & Precision Engineered
440C stainless steel balls from Atlas Ball & Bearing are the industry standard for applications requiring exceptional hardness, superior wear resistance, and strong corrosion protection. As a high-carbon martensitic stainless steel, 440C offers the highest hardness of all stainless grades—making it ideal for high-load bearings, precision mechanical components, and demanding industrial assemblies.
When hardened, 440C develops excellent fatigue life, dimensional stability, and resistance to abrasion. These properties make it the preferred choice for aerospace, medical, automotive, military, and high-precision bearing applications.
150
Precision Ball Diameter
Why Choose 440C Stainless Steel Balls?
440C stainless steel is one of the highest-performing stainless bearing materials available. With its high carbon content, the grade can be hardened to extremely high levels, offering outstanding wear resistance and mechanical strength while still maintaining useful corrosion protection.
Key Benefits
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Highest hardness of all stainless grades after heat treatment
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Exceptional wear resistance and fatigue strength
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Strong corrosion resistance in fresh water, mild chemicals & normal atmospheres
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Superior performance under high loads and high-speed rotations
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Excellent dimensional stability
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Ideal for precision-grade bearings
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Long service life in demanding environments
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Reliable mechanical properties under stress, impact, and friction
Manufacturing & Supply
We are capable of manufacturing and supplying loose 440C stainless steel balls in nearly every variation of grade, maintaining an extensive stock with sizes ranging from 0.2mm to 150mm in diameter.
Please feel free to rate our products and service or send us your comments by using our form opposite →
Additionally, we offer a bespoke ball manufacturing service, which follows the same process controls and traceability but uses a customer’s own material. For further details, please email us or call +44 (0) 1922 710515.
Applications
440C stainless steel balls are used in applications where extreme hardness, precision, and wear resistance are essential.
Typical applications include:
High-precision ball bearings
Aerospace and defence components
Medical instruments and devices
High-speed mechanical assemblies
Measuring instruments and metrology equipment
Valves, pumps & high-pressure systems
Robotics and automated machinery
Automotive bearings & motion systems
Environments requiring high hardness with moderate corrosion resistance
440C is the go-to material for demanding, high-stress applications requiring a precision-engineered stainless steel ball with exceptional wear resistance.
Why Atlas Ball & Bearing?
UK-based manufacturer and supplier of high-performance stainless steel balls
Extensive stock of 440C stainless steel across a wide range of diameters
Certified precision engineering and consistent product accuracy
Technical guidance for aerospace, medical & industrial applications
Fast UK and international delivery
Bespoke manufacturing available to exact specifications
Full traceability and quality assurance
Related Materials
Explore other stainless steel and premium ball materials in the Atlas Ball range:
304 Stainless Steel Balls
316 Stainless Steel Balls
420 Stainless Steel Balls
Useful terms and definitions
Batch or Lot:
A defined quantity of balls manufactured under conditions presumed to be uniform and which is considered an entity.
Nominal Ball Diameter:
The diameter value that is used for the general identification of a ball size.
Single Ball Diameter:
The distance between two parallel planes tangential to the actual ball surface.
Diameter Tolerance per Batch:
The allowed difference between the smallest measured ball diameter and the largest ball diameter within the same batch or lot quantity.
Sphericity:
A measure of roundness expressed as the difference between the measured roundness of a ball and a theoretically perfectly round ball.
Surface Finish or Roughness:
A measure of the texture of a surface. It is quantified by the vertical deviations of the actual surface from its ideal form. If these deviations are large, the surface is rough; if they are small, the surface is smooth.
Ball Grades
| Grade | Diameter Tolerance per Ball | Sphericity | Diameter Tolerance per Unit Container | Basic Diameter Tolerance | Maximum Surface Roughness Micro | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| Inch | µ | Inch | µ | Inch | µ | Inch | µ | Inch | µ | |
| 3 | .000003 | 0.076 | .000003 | 0.076 | .000005 | 0.127 | ±.00003 | ± 0.076 | 0.5 | 0.013 |
| More details about Grade 3... | ||||||||||
| 5 | .000005 | 0.127 | .000005 | 0.127 | .00001 | 0.25 | ±.00005 | ± 0.127 | 0.8 | 0.02 |
| More details about Grade 5... | ||||||||||
| 10 | .000010 | 0.25 | .000010 | 0.25 | .00002 | 0.51 | ±.0001 | ± 2.5 | 1.0 | 0.025 |
| More details about Grade 10... | ||||||||||
| 15 | .000015 | 0.38 | .000015 | 0.38 | .00003 | 0.76 | ±.0001 | ± 2.5 | 1.2 | 0.03 |
| More details about Grade 15... | ||||||||||
| 25 | .000025 | 0.63 | .000025 | 0.63 | .00005 | 1.27 | ±.0001 | ± 2.5 | 1.5 | 0.038 |
| More details about Grade 25... | ||||||||||
| 50 | .00005 | 1.27 | .00005 | 1.27 | .0001 | 2.5 | ±.0002 | ± 5 | 3.0 | 0.075 |
| More details about Grade 50... | ||||||||||
| 100 | .0001 | 2.5 | .0001 | 2.5 | .0002 | 5 | ±.0005 | ± 5 | 5.0 | 0.125 |
| More details about Grade 100... | ||||||||||
| 200 | .0002 | 5 | .0002 | 5 | .0004 | 10 | ±.0010 | ± 10 | 8.0 | 0.2 |
| More details about Grade 200... | ||||||||||
| 300 | .0003 | 7.5 | .0003 | 7.5 | .0006 | 15 | ±.0015 | ± 37.5 | N/A | N/A |
| More details about Grade 300... | ||||||||||
| 500 | .0005 | 12.5 | .0005 | 12.5 | .001 | 25 | ±.002 | ± 50 | N/A | N/A |
| More details about Grade 500... | ||||||||||
| 1000 | .001 | 25 | .001 | 25 | .002 | 50 | ±.005 | ± 125 | Not Applicable | Not Applicable |
| More details about Grade 1000... | ||||||||||
| 2000 | .002 | 50 | .002 | 50 | .004 | 100 | ±.005 | ± 125 | N/A | N/A |
| More details about Grade 2000... | ||||||||||
Sample Our Work!
Take the first step towards precision and quality with our expert services. At Atlas Ball & Bearing, we’re committed to delivering top-notch precision balls and rollers for a wide range of industries, including gas, oil, medical, and transportation. Our dedicated team is ready to assist you with custom solutions tailored to your specific needs. Experience the Atlas Ball & Bearing difference now!