Ball Screws
High-Precision C2/C3 | Diameter 8-100mm | DIN 69051
High-efficiency motion conversion from rotary to linear with >90% mechanical efficiency. FCD, FC/FCZ, FY/FYZ, FYD, and FYB series covering external and internal recirculation types. Engineered for CNC machine tools, industrial robots, semiconductor equipment, aerospace actuators, and precision automation.
What Is a Ball Screw?
A ball screw is a mechanical linear actuator that converts rotary motion into linear motion with minimal friction. It consists of a threaded shaft (screw), a nut containing recirculating ball bearings, and precision-ground raceways. As the screw rotates, balls roll along the helical groove, transferring motion through the nut while providing extremely low rolling resistance.
Ball screws achieve >90% mechanical efficiency — far superior to traditional lead screws (typically 20-40%). They deliver exceptional positioning accuracy, repeatability down to the micron level, long service life under high load, and smooth operation across a wide speed range. These characteristics make ball screws the motion backbone of precision machinery worldwide.
Low Friction
Rolling contact reduces energy loss
High Accuracy
Micron-level positioning repeatability
Long Service Life
Hardened raceways resist wear
High Speed Capability
Smooth operation across wide RPM range
Ball Screw Series Overview
Five distinct ground ball screw series covering external and internal recirculation types, and a broad dimensional range to meet every precision motion requirement.
FCD Series Ball Screws
Double-nut preloaded design for zero-backlash applications. External tube-type recirculation ensures smooth ball return and high-speed capability. Ideal for CNC machining centers and high-precision positioning stages requiring maximum rigidity.
- Diameter: 16-80mm
- Lead: 5-40mm
- Accuracy: C2, C3
FC (FCZ) Series Ball Screws
Single-nut design with internal deflector recirculation for compact axial space. FCZ variant features optimized deflector geometry for reduced noise and improved high-speed performance. Excellent choice for general-purpose CNC feed axes and automation equipment.
- Diameter: 12-63mm
- Lead: 4-32mm
- Accuracy: C2, C3
FY (FYZ) Series Ball Screws
High-precision ground ball screws with internal recirculation. C2/C3 accuracy for demanding linear motion applications. Widely used in CNC machine tools, precision automation, semiconductor equipment, and general industrial actuation.
- Diameter: 8-63mm
- Lead: 4-40mm
- Accuracy: C2, C3
FYD Series Ball Screws
Flanged-nut ground ball screw series engineered for simple mounting and reduced assembly time. Pre-drilled flange bolt pattern matches standard industry mounting interfaces. Popular choice for linear modules and single-axis actuators.
- Diameter: 15-50mm
- Lead: 5-25mm
- Accuracy: C3
FYB Series Ball Screws
Micro ball screw series designed for small-diameter, miniature applications. Available down to 8mm diameter for compact precision mechanisms in semiconductor equipment, medical devices, and laboratory automation where space is critical.
- Diameter: 8-25mm
- Lead: 2-10mm
- Accuracy: C2, C3
How to Select the Right Ball Screw
Five key parameters to specify for optimal ball screw performance in your application
Nominal Diameter & Lead
Diameter (O8-O100mm) determines load capacity — larger diameters handle higher axial loads. Lead (typically 5-40mm) determines linear speed: speed = lead x RPM. Match the diameter/lead combination to your required travel speed and load. FCD series offers the widest diameter range for heavy-duty applications.
Accuracy Grade — C2, C3, C5, or C7?
C2 (DIN 69051 Class 2): ultra-precision, <5 micron lead error per 300mm. For semiconductor wafer stages, precision measurement. C3 (Class 3): high precision, <12 micron. Standard for CNC machine tools. C5 (Class 5): general precision, <23 micron. For industrial automation. C7 (Class 7): rolled screws, <52 micron. Economical for material handling. Luoyang Songju supplies C2 and C3 precision ground screws as standard.
Preload Class — Eliminate Backlash
Standard (no preload): acceptable for general positioning where reversal error is tolerated. Light preload (P1): eliminates backlash with minimal friction increase — preferred for most CNC applications. Medium preload (P2): high stiffness for heavy cutting loads. Heavy preload (P3): maximum rigidity, used in high-precision grinding machines. FYD and FYB series feature double-nut designs for preload adjustment.
Nut Type — Single, Double, or Cylindrical?
Single nut: compact, economical. FC and FY series for standard applications. Double nut (FYD, FYB): preload via spacer between two nuts — eliminates backlash and increases stiffness. Ideal for high-precision machining. Cylindrical nut (FCD): integrated flange design for heavy-duty machine tools where maximum rigidity is essential. FCZ/FYZ: flange nut variants for easy bolt-on mounting.
End Machining & Support Bearings
Ball screw ends can be machined to your specifications — standard journal, threaded, or keyed configurations. Support bearings (angular contact or ZKLF series) should be selected to match the screw diameter and axial load. We offer complete ball screw + bearing support packages pre-assembled and tested for plug-and-play installation.
Ball Screw Classification
Understanding the key design parameters and manufacturing methods helps you select the optimal ball screw for your specific application requirements.
Classification by Ball Recirculation Type
External Recirculation
Balls return to the starting end through an external tube or deflector mounted outside the nut body. This design allows for a larger number of ball circuits and higher load capacity. The return tube is typically made of hardened steel or engineering plastic for smooth transition.
Internal Recirculation
Balls recirculate inside the nut body through internal passages or deflectors, resulting in a compact and streamlined nut profile. The internal design reduces overall dimensions, making it suitable for applications with limited installation space.
Classification by Nut Design
| Nut Type | Description | Typical Series | Key Benefit |
|---|---|---|---|
| Single Nut | One nut body with single ball circuit. Simple construction with standard backlash. | FC, FY, FYD | Cost-effective, compact |
| Double Nut (Preloaded) | Two nuts with preload spacer or spring mechanism. Eliminates axial backlash for high-precision bidirectional positioning. | FCD | Zero backlash, maximum rigidity |
| Flanged Nut | Nut body with integrated mounting flange. Pre-drilled bolt pattern simplifies installation and alignment. | FYD, Select FY | Easy mounting, reduced assembly time |
| Cylindrical Nut | Smooth cylindrical nut body. Retained by external housing or bearing support. Most common industrial configuration. | FC, FY, FYB | Versatile, widely compatible |
Classification by Manufacturing Method
Ground Ball Screws
C2, C3Precision-ground raceways using CNC thread grinding machines. Each screw is individually ground to achieve micron-level lead accuracy on the full travel length. Surface roughness typically Ra 0.2-0.4 um for ultra-smooth ball travel.
- Lead accuracy: 0.003-0.023mm per 300mm (C3)
- Ideal for CNC machine tools, CMM, semiconductor
- Series: FCD, FC, FCZ, FYB (C3)
Ground Ball Screws
C2, C3Thread formed by precision CNC thread grinding on hardened alloy steel screw blanks. Each screw is individually ground between centers to achieve lead accuracy of 0.003-0.023mm per 300mm. Surface finish Ra 0.2-0.4 um for ultra-smooth ball travel and long service life under continuous high-load operation.
- Lead accuracy: 0.003-0.023mm per 300mm (C2-C3)
- Ideal for CNC machine tools, semiconductor, precision stages
- Series: FCD, FC, FY, FYD, FYB (C2/C3)
Industries We Serve
Luoyang Songju ball screws power precision motion across a diverse range of demanding industries worldwide.
CNC Machine Tools
Feed axes for machining centers, turning centers, grinding machines, and EDM. Ground C2/C3 screws ensure micron-level positioning accuracy for tight-tolerance machining.
Industrial Robots
Joint actuators for articulated robots, Cartesian gantry systems, and SCARA robots. High efficiency reduces motor size and energy consumption.
Semiconductor
Wafer handling stages, wire bonders, lithography positioning systems. Miniature FYB series with C3 accuracy for cleanroom environments.
Aerospace
Flight control actuators, landing gear mechanisms, satellite deployment systems. High-reliability ground ball screws with full material traceability.
Medical Devices
CT scanner patient tables, surgical robots, diagnostic positioning systems. Smooth, silent operation with corrosion-resistant options available.
Automotive
Electric power steering, brake-by-wire actuators, production line transfer systems. ground C2/C3 screws for high-precision, high-volume applications.
Printing & Packaging
Print head positioning, die-cutting presses, labeling machines. FYD flanged-nut series for quick installation and reduced downtime.
Laboratory Automation
Liquid handling robots, sample positioning stages, microplate readers. FYB micro ball screws for compact precision mechanisms in lab instruments.
Series Selection Guide
Compare our five ball screw series side by side to find the best match for your application.
| Series | Diameter Range | Lead Range | Accuracy | Recirculation | Nut Type | Best For |
|---|---|---|---|---|---|---|
| FCD | 16-80mm | 5-40mm | C2, C3 | External (Tube) | Double (Preloaded) | CNC machining centers, zero-backlash |
| FC (FCZ) | 12-63mm | 4-32mm | C2, C3 | Internal (Deflector) | Single / Cylindrical | CNC feed axes, general precision |
| FY (FYZ) | 8-63mm | 4-40mm | C2, C3 | Internal | Single / Cylindrical | General CNC feed axes, automation |
| FYD | 15-50mm | 5-25mm | C3 | Internal | Single (Flanged) | Linear modules, quick-install |
| FYB | 8-25mm | 2-10mm | C2, C3 | Internal | Single (Cylindrical) | Miniature, semiconductor, medical |
Need Help Selecting a Ball Screw?
Our application engineers provide free technical consultation, 3D CAD models, sizing calculations, and competitive quotations. Tell us your application requirements and we will recommend the optimal ball screw series.
Ball Screw FAQ
What accuracy grades do Songju ball screws come in?
We offer C2 (IT2), C3 (IT3), and C5 (IT5) accuracy grades per DIN 69051. C2 grade provides +/-5um/300mm lead deviation, suitable for ultra-precision CNC machines and semiconductor equipment. C3 grade (+/-8um) is the most popular choice for general CNC machine tools. C5 grade (+/-18um) is cost-effective for positioning applications with moderate accuracy requirements.
What is the difference between internal and external return ball screws?
Internal return (FC, FCD series) recirculates balls within the nut body via internal deflectors, providing compact design, lower noise, and suitability for medium-speed applications. External return (FY, FYZ, FYD, FYB series) uses external return tubes, offering higher load capacity, better heat dissipation, and suitability for high-speed and large-lead applications. Select based on speed, load, and space constraints.
What preload options are available?
Double nut spacer preload (FCD, FYD series) provides adjustable rigidity via precision-ground spacer between two nuts. Oversized ball preload offers simpler single-nut design with lower cost. Spring preload maintains constant preload force even with wear. For most CNC applications, double nut spacer preload provides the best combination of rigidity, accuracy retention, and service life.
How do I calculate ball screw life expectancy?
Ball screw life is calculated using the L10 formula: L10 = (C/P)^3 x 10^6 revolutions, where C is dynamic load rating and P is equivalent axial load. Factors affecting life include: preload level, lubrication quality, contamination, duty cycle, and operating speed. Our engineering team provides detailed life calculations based on your application parameters. Typical CNC machine tool ball screws achieve 15,000-30,000 operating hours with proper maintenance.
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