Precision Ball Manufacturing
STR Industries is a manufacturer of high-quality precision balls suitable for use in a wide range of applications, including art design, product manufacturing, finishing operations, and more. Equipped with over five decades of experience manufacturing steel balls, our team has the knowledge and skills to design and deliver high-precision, high-accuracy balls in a variety of shapes, sizes, and materials. Below we provide an overview of our ball manufacturing offerings, which includes:
Steel Balls
Steel balls are commonly used as rolling mechanisms and other spherical components in products such as automotive bearings, casters, rollers, sliders, sports equipment, and toys.
When selecting a steel ball for a project, it is important to consider performance and application-specific requirements, as these factors determine what material properties (and, therefore, what materials) are required. Each steel grade offers distinct characteristics that make it suitable for different applications.
Our steel balls are available in the following grades:
Grade and Tolerance – Inches
| Size Range | Deviation from Spherical Range | Lot Diameter Variation | Allowable Ball Gage Variation | Nominal Ball Diameter Tolerance | Marking Increments | Maximum Surface Roughness 1 in Micro inches “Ra” |
|---|---|---|---|---|---|---|
| .006 - 2" | 0.000003 | 0.000003 | ±0.00003 | - | 0.00001 | 0.5 |
| .006 - 6" | 0.000005 | 0.000005 | ±0.00005 | - | 0.00001 | 0.8 |
| .006 - 10" | 0.00001 | 0.000010 | ±0.00005 | - | 0.00001 | 1.0 |
| .006 - 10" | 0.000025 | 0.000025 | ±0.00010 | - | 0.00001 | 2.0 |
| .006 - 10" | 0.00005 | 0.000050 | - | ±0.0002 | 0.00005 | 3.0 |
| .006 - 10" | 0.0001 | 0.0001 | - | ±0.0005 | - | 5.0 |
| .006 - 10" | 0.0002 | 0.0002 | - | ±0.001 | - | 8.0 |
| .006 - 10" | 0.001 | 0.001 | - | ±0.005 | - | - |
Key Precision Ball Terminology
When choosing precision balls for your application, it’s essential to understand the core measurement terms used to describe their manufacturing quality:
- Allowable Deviation from Spherical Form:
This refers to the largest difference in radius measured in any direction between the actual surface of the ball and a perfectly circumscribed sphere. In simpler terms, it indicates how closely the ball matches a true sphere—critical for ensuring smooth operation in high-precision assemblies. - Surface Roughness:
This describes the tiny, localized variations on the ball’s surface texture, excluding larger form deviations or overall waviness. These microscopic irregularities can impact both wear resistance and how the ball interacts with mating components. - Basic Ball Diameter & Tolerance:
The basic diameter is the target measurement specified for the ball. Tolerance defines the maximum permitted variation from this nominal size, ensuring that every ball falls within strict dimensional limits, whether you’re working in metric or standard units.
Understanding these definitions helps in selecting the right ball for your application’s performance and durability requirements.
Stainless steel is a steel alloy consisting of approximately 89% steel and 11% chromium. It demonstrates resistance to corrosion and staining, both of which make it suitable for applications where cleanliness and corrosion resistance are critical (e.g., buildings, cutlery, and medical devices). There are two variations available: hardened and non-hardened.
- Hardened stainless steel balls are fabricated using Martensitic processes, which increase their carbon level and make them more durable and wear-resistant. They are generally used as ball bearings in high-friction devices, such as lighters, pens, and pumps.
We offer the following types of hardened stainless steel balls:
– AISI 420A/420B stainless steel balls
– AISI 420C stainless steel balls
– AISI 440C stainless steel balls
Other notable Martensitic stainless steels used for hardened balls include 410, 416, 440A, and 440V. These steels are valued for their combination of hardness and moderate corrosion resistance, making them reliable for demanding mechanical environments.
- Non-hardened stainless steel balls are manufactured with Austenitic processes, which introduce nickel and carbon into the material. While this type of steel is more workable than its hardened counterpart, it tends to be less corrosion resistant. These balls are generally used in electronic components.
We offer the following selection of non-hardened stainless steel balls:- AISI 204 Cu stainless steel balls
- AISI 302/304/304L stainless steel balls
- AISI 303 stainless steel balls
- AISI 316/316L stainless steel balls
- AISI 316Ti stainless steel balls
- AISI 430/430F stainless steel balls
- AISI 904L stainless steel balls
- Super duplex 2507 stainless steel balls
Beyond stainless steel, ball bearings are also manufactured from a wide range of alloys to suit specific operating environments and requirements:
- Alloy Steels: Chrome Steel (52100), M50, M2, 4130, 4140, 4340, Graph Mo, commonly used where high strength and toughness are prioritized.
- Carbon Steels: Soft and hard carbon variants, as well as cast iron and carburized grades like 1010 1018 1065 1085 , are selected for cost-effectiveness and adequate mechanical properties in less demanding applications.
- Copper Alloys and Aluminum Alloys: Balls made from copper grades (101, 102, 110), brass (C260, C360), bronze (C464, C510, C624, C630), and beryllium copper (C172) are valued for their electrical conductivity and corrosion resistance. Aluminum alloy balls (1100, 2011, 2017, 2024, 5052, 5056, 6061, 7075, 2219) provide lightweight options for applications where reducing mass is critical.
This comprehensive selection of ball materials ensures that, whether your requirements prioritize strength, corrosion resistance, electrical conductivity, or specialized environmental performance, there is a suitable material choice available.
Typical Tolerance Values for Ball Grades
Precision balls are manufactured to meet rigorous quality standards, with each grade reflecting a specific set of tolerance values. Understanding these tolerances is vital when selecting the right ball for your application, whether you’re specifying them for a watch, pump, or precision bearing.
Here’s a quick overview of the most common ball grades and their corresponding tolerances:
- Grade 3:
- Maximum deviation from spherical form: 0.000003″
- Surface roughness: 0.5 micro-inches (arithmetical average)
- Diameter tolerance: ±0.000030″
- Grade 5:
- Sphericity: 0.000005″
- Surface roughness: 0.8 micro-inches
- Diameter tolerance: ±0.000050″
- Grade 10:
- Sphericity: 0.000010″
- Surface roughness: 1.0 micro-inch
- Diameter tolerance: ±0.0001″
- Grade 16, 24, and 25:
- Sphericity ranges from 0.000016″ to 0.000025″
- Surface roughness: around 2.0 micro-inches
- Diameter tolerance: ±0.0001″
- Grade 48 and 50:
- Sphericity: up to 0.000050″
- Surface roughness: 3.0 micro-inches
- Diameter tolerance: ±0.0002″
- Grades 100 to 1000:
- Sphericity spans from 0.0001″ (Grade 100) up to 0.001″ (Grade 1000)
- Surface roughness increases to 8.0 micro-inches and above
- Diameter tolerance widens from ±0.0005″ (Grade 100) to ±0.005″ (Grade 1000)
These tolerances are established in accordance with leading international standards, such as those defined by ASTM and ISO. When precision is paramount—think aerospace instruments or high-speed bearings—lower number grades offer tighter tolerances and smoother surfaces. For less demanding roles, higher grades provide durability and cost-effectiveness.
Carefully matching the ball grade to the application’s requirements ensures optimal performance and long-term reliability.
Industry Standards for Ball Grade Tolerance
When it comes to precision metal balls, strict industry standards ensure quality and consistency across applications. Among the most widely recognized are ASTM F2215 and ANSI/ABMA/ISO 3290, which specify grading criteria for spherical form, surface roughness, and dimensional accuracy.
Key Tolerance Factors
Ball grade tolerance is determined by several measurable characteristics, including:
- Deviation from Spherical Form:
This refers to the maximum allowable variance between the actual surface of the ball and a perfect sphere, measured radially in any direction. - Surface Roughness:
This metric captures the tiny surface irregularities that don’t affect the ball’s overall shape but do impact how smooth the surface feels and performs. - Diameter Tolerance:
Here, standards define how much a ball’s average diameter can differ from its nominal (specified) size, ensuring consistency in fit and performance.
Common Ball Grades and Their Tolerances
Ball grades describe the level of precision, with lower numbers corresponding to tighter tolerances. Here’s a helpful breakdown of common ball grades and their associated tolerances:
| Ball Grade | Spherical Deviation (inches) | Surface Roughness (µin) | Diameter Tolerance (inches) |
| 3 | 0.000003 | 0.5 | 0.000030 |
| 5 | 0.000005 | 0.8 | 0.000050 |
| 10 | 0.000010 | 1.0 | 0.000100 |
| 25 | 0.000025 | 2.0 | 0.000100 |
| 50 | 0.000050 | 3.0 | 0.000200 |
| 100 | 0.000100 | 5.0 | 0.000500 |
| 200 | 0.000200 | 8.0 | 0.001000 |
| 1000 | 0.001000 | — | 0.005000 |
The result? Whether you require ultra-precise balls for aerospace or bearings for industrial machinery, these standards ensure each ball meets stringent specifications for roundness, smoothness, and size.
These standardized grades make it easier to select the right balls for demanding applications—whether you’re in manufacturing, engineering, or scientific research.
Bearing Steel
Bearing steel balls are fabricated from low-alloy hardened chromium steel, which exhibits exceptional wear resistance, hardness, surface finishing, and dimensional stability. These qualities make such balls well-suited for use in a variety of industrial and commercial applications, ranging from automobile components to conveyor belts to pumps and valves.
We manufacture the following bearing steel balls:
- AISI 52100 100Cr6 chrome steel balls
- Low-noise AISI 52100 high-precision chrome steel balls
- 100CrMn6 chrome steel balls
- 100CrMo7-3 chrome steel balls
- 100CrMnMo8 chrome steel balls
Carbon Steel
Carbon steel balls consist of steel with a carbon content of less than 0.093%. The presence of carbon provides a hardening effect that adds strength and durability to the material without requiring costly hardening operations. These high-strength balls are commonly used in furniture items, sliding rails, welding appliances, polishing and milling machines, and peening applications.
We offer the following carbon steel ball options:
- AISI 1010/1015 low-carbon steel cemented balls
- AISI 1010/1015 low soft unhardened carbon steel balls
- AISI 1085 high-carbon steel balls
Tool Steel
Tool steel is a carbon alloy steel that is particularly well-suited for tool fabrication due to its exceptional hardness, abrasion resistance, and ability to preserve its shape at increased temperatures. Balls made from this material are often employed as bearing components in high-temperature equipment and systems such as aircraft and rocket engines.
The tool steel balls we supply include:
- AISI D2 tool steel balls
- AISI M2 tool steel balls
- AISI M50 tool steel balls
- AISI T15 tool steel balls
- S-2 ROCKBIT tool steel shock-resistant balls
Other Metal Alloy Balls
A metal alloy is a metal combined with one or more other metal or non-metal elements. The resulting material tends to have enhanced physical and chemical properties, including improved strength, hardness, corrosion resistance, and formability. For precision ball manufacturing, some of the most commonly employed metal alloys are:
Aluminum
Aluminum alloy balls demonstrate excellent strength, corrosion resistance, and hard-wearing characteristics. Additionally, their surfaces can easily be treated to have a smooth finish. They are frequently used in special bearings, valves, automotive and electric safety devices, and aviation and aerospace components. When considering aluminum alloy balls for an application, it is important to keep in mind that they are vulnerable to cracking and pitting in chloride-rich environments.
We manufacture the following types of aluminum alloy balls:
- Aluminum alloy balls Series 1XXX
- Aluminum alloy balls Series 2XXX
- Aluminum alloy balls Series 3XXX
- Aluminum alloy balls Series 5XXX
- Aluminum alloy balls Series 6XXX
- Aluminum alloy balls Series 7XXX
Brass-Copper-Bronze Alloy
Brass, bronze, and other copper alloys are also used in precision ball manufacturing. They exhibit a variety of advantageous properties, including corrosion resistance, workability, durability, and visually appealing surface finishes.
We supply the following metal alloy balls:
- Brass balls
- Bronze aluminum alloy balls
- Bronze aluminum nickel alloy balls
- Copper balls
- Copper beryllium alloy balls
- Phosphor bronze alloy balls
Plastic Balls
The properties of plastics make them well-suited for the fabrication of balls with low density, excellent corrosion resistance, and high durability. Depending on the type of feedstock used, the balls may also demonstrate other performance characteristics, such as resistance to damage from abrasion or high temperatures. Some common uses for plastic balls include appliances, low-load bearings, furniture sliding rails, medical and laboratory instruments, and pumps and valves.
We offer an extensive selection of plastic balls made from various high-quality feedstocks, including:
- ABS balls
- Acrylic (PMMA) balls
- Composite plastic balls
- Delrin® (POM) balls
- Glass-filled plastic balls
- High-density polyethylene (HDPE) balls
- Hytrel® (TPE) balls
- Low-density polyethylene (LDPE) balls
- Machined rod end plastic balls
- Nylon 6/Nylon 6.6 (PA 6/PA 6.6) balls
- PEEK balls
- Phenolic resin balls
- Polycarbonate (PC) balls
- Polyketone (PK) balls
- Polypropylene (PP) balls
- Polystyrene (PS) balls
- Polyurethane (TPU) balls
- PVC balls
- PVDF balls
- Teflon® (PTFE) balls
- Torlon® balls
- Ultra-high molecular weight (UHMW) polyethylene balls
- Vespel® balls
In addition to these, plastic balls are also available in a range of specialty polymers to suit demanding environments. Materials such as Acetal (Delrin®), PVDF (Kynar®), and Nylons are chosen for their unique balance of strength, chemical resistance, and temperature tolerance. These options enhance performance in applications where traditional plastics might fall short, such as in aggressive chemical processing or high-precision laboratory instruments.
Ceramic Balls
Ceramic balls are constructed from a wide range of materials, depending on the needs of the application. In addition to being extremely resistant to corrosion and wear, they require minimal lubrication to operate smoothly and efficiently and are exceptionally tolerant of acidic, alkaline, and high-temperature conditions. These characteristics make them well-suited for a number of high-performance applications, including flow valves in chemical systems, pumps, water treatment systems, and special bearings.
We fabricate the following types of ceramic balls:
- Aluminum oxide (Al2O3) balls
- Ruby balls
- Sapphire balls
- Silicon carbide (SiC) balls
- Silicon nitride (Si3N4) balls
- Zirconium oxide (ZrO2) balls
- Zirconia toughened alumina (ZTA) ceramic balls
Beyond these, ceramic balls are also produced from advanced compositions such as titanium carbide, alumina (90%), zirconia stabilized with magnesium or yttrium, and zirconium carbide. Each material is tailored for specific applications: for example, silicon nitride and silicon carbide excel in high-speed bearings and valves, while ruby and sapphire are chosen for their optical clarity in precision instruments. Boron nitride and other specialized ceramics further broaden the range, offering solutions for extreme environments where both chemical and mechanical stability are paramount.
Glass Balls
Glass balls offer corrosion resistance and electrical insulating properties. Additionally, they are available in transparent variations for use in optical devices. Typical applications include medical devices, pumps, gauges, and water treatment bearings.
Our glass ball selection includes:
- Black glass balls
- Borosilicate glass balls
- Quartz (SiO2) balls
- Soda lime glass balls
For specialized needs, glass balls are also manufactured from fused silica and are available in varieties such as borosilicate for thermal shock resistance and soda lime for cost-effective utility. Quartz balls provide exceptional purity and stability for scientific and optical applications, while fused silica excels in environments requiring high UV and chemical resistance.
This diversity ensures that glass balls can accommodate a wide array of technical demands, from laboratory equipment and instrumentation to flow control and precision measurement.
Why Choose STR Industries for Your Precision Ball Manufacturing Needs?
Whether they are made from metal, plastic, glass, or ceramic, precision balls play a critical role in many industrial devices, equipment, and systems. For all of your precision ball needs, turn to the experts at STR Industries.
Over our 50 years in business, we built an extensive selection of high-quality ball products suitable for use in some of the most critical industrial and commercial applications. Our team works closely with customers to design and develop precision ball solutions tailored to meet exacting specifications.
Have unique requirements? No problem. Just let us know what you need, and we will do what it takes to meet your exact precision ball specifications, whether your project demands a specialized alloy, a non-standard size, or tight tolerances for challenging environments.
To learn more about our precision ball manufacturing capabilities, contact us today.