FYD Series
Ball Screws — Double Nut, External Return
The ultimate ball screw combining external return tube load capacity with double-nut zero backlash. C2/C3 ground for the most demanding precision machining applications.
FYD Series / Ball Screws — Double Nut, External Return
The FYD Series combines the high load capacity of external ball recirculation tubes with the zero-backlash performance of a double-nut preload configuration. Two nuts are precision-matched with a spacer element that applies contground preload, eliminating axial clearance while the external tube design simultaneously enables maximum ball diameters for superior load ratings. This dual-benefit architecture makes FYD the highest-capacity zero-backlash ball screw in Luoyang Songju's product line.
Ground to C2 or C3 accuracy, FYD ball screws deliver the positioning precision required by high-end CNC grinding machines, precision boring mills, and ultra-accurate positioning stages -- all while supporting the heavy cutting forces these applications generate. Available in diameters from 20mm to 80mm with leads from 5mm to 32mm. The external tube design provides easy access for inspection and maintenance, reducing long-term service costs in high-utilization production environments.
Download Drawing Get a QuoteDetailed Parameters
| Series | FYD (Double Nut, External Recirculation) |
| Nut Type | Double nut with spacer preload |
| Ball Return | External recirculation tube |
| Accuracy Grades | C2, C3 (ground) |
| Preload | Spacer preload — zero backlash |
| Screw Diameter | 20mm, 25mm, 32mm, 40mm, 50mm, 63mm, 80mm |
| Lead Range | 5mm, 10mm, 16mm, 20mm, 25mm, 32mm |
| Screw Material | Gcr15 bearing steel |
| Screw Hardness | 58–62 HRC |
| Axial Clearance | Zero (preloaded) |
| Load Capacity | Very High — double nut + large ball combination |
| Rigidity | Very High |
| Max DN Value | 120,000 |
| Max Screw Length | 6000mm |
| Operating Temperature | -20°C to +80°C |
| Lubrication | Grease nipple (dual ports) |
| Seal Type | Heavy-duty wiper seals |
| Application | High-Precision CNC, Grinding Machines, Boring Mills, Ultra-Accurate Stages |
Available Options & Customizations
- Ceramic ball upgrade
- Custom end machining
- Increased preload for extreme rigidity
- Integrated cooling channels
- Position feedback sensor mounts
Why Choose FYD Series Ball Screws
The FYD Series represents the pinnacle of ball screw engineering — combining zero-backlash double-nut preload with the high load capacity of external recirculation tubes for the most demanding CNC applications.
Zero Backlash + High Load
The unique dual-benefit design eliminates axial play while simultaneously maximizing load capacity — a combination no single-nut or internal-return screw can match.
Double Nut Preload
Two precision-matched nuts with a contground spacer apply uniform preload across the full stroke, eliminating backlash without introducing torque variation.
External Tube Access
External recirculation tubes allow quick visual inspection and maintenance without disassembly, reducing service time and extending operational availability.
Ground Precision
C2 or C3 ground accuracy ensures the positioning repeatability required by high-end CNC grinding and boring applications with sub-micron tolerances.
Maximum Rigidity
The dual-nut configuration combined with the largest possible ball diameters delivers the highest axial and radial rigidity available in any Songju ball screw series.
Heavy-Duty Sealing
Reinforced wiper seals protect the precision-ground raceways from coolant, swarf, and abrasive dust in the most aggressive production machining environments.
Need Maximum Precision Ball Screws?
Tell us your precision requirements, load conditions, and stroke length. Our engineers will configure the optimal FYD Series double-nut ball screw with full technical documentation, accuracy certificates, and competitive pricing. 24-hour response guaranteed.