MOSIONX (Taiwan Global Transmission, formerly TBI MOTION) SFAR / SFA series ball screws now cover the Φ50 shaft diameter. Φ50 is not a single specification: it is offered in five lead steps — 5 / 10 / 20 / 50 / 100 mm. Within the same lead, rated loads can differ by several times between nut series, so always select by the specific model's parameters.
To meet the demand for heavy-load, long-stroke automation equipment, the Φ50 family gives you one shaft diameter that spans the mid- to heavy-load range. This page lists the spec table, compares Φ50 against Φ40, and explains the speed limits so you can pick the right model.
| Lead | Available series | Ball diameter | Dynamic load rating | Static load rating |
|---|---|---|---|---|
| 5 mm | SFA / SFV | Φ3.175 | 21.6 – 26.5 kN | 93.6 – 118.2 kN |
| 10 mm | SFA / SFNU / SFNI / SFV / OFI / OFU / OFV | Φ6.35 | 55.3 – 68.9 kN | 175.1 – 230.8 kN |
| 20 mm | SFA / SFNU / SFV | Φ6.35 – Φ9.525 | 56.4 – 71.9 kN | 181.3 – 221.5 kN |
| 50 mm | SFA / SFY / SFYA | Φ6.35 – Φ7.938 | 28.9 – 103.5 kN | 85.8 – 335.2 kN |
| 100 mm | SFY / SFYA | Φ7.938 | 33.3 – 66.9 kN | 97.9 – 220.2 kN |
The highest values in the family occur at SFYA05050-5.6 / SFY05050-5.6 (50 mm lead): dynamic load rating 103.5 kN, static load rating 335.2 kN, axial rigidity 131 kgf/μm. Values in the table are converted from the catalog's kgf ratings (1 kN = 1000 / 9.80665 kgf).
The gain depends on the series and lead — there is no single number:
Takeaway: a larger shaft diameter does not automatically mean a higher load rating — the 5 mm lead step is the counterexample. Heavy-load selection must compare specific models one by one, not just look at the shaft diameter.
The maximum speed of a Φ50 screw is bounded by the smaller of two conditions:
So “Φ50 up to 3000 rpm” only holds for short-stroke, high-speed configurations; long-stroke duty must be calculated for critical speed separately.
Dynamic load rating 21.6 – 103.5 kN, static load rating 85.8 – 335.2 kN — one shaft diameter covers the mid- to heavy-load range. The 50 mm lead SFYA05050-5.6 is the highest-capacity step in the family.
C5 ground-grade products are finished by precision grinding; lead accuracy reaches ±0.005 mm / 300 mm, with excellent positioning and repeatability.
Internal-recirculation design gives smooth ball circulation; operating noise is below 60 dB(A) at 1 m.
The raceway is specially heat-treated to HRC 58–62, with an effective hardened-layer depth ≥ 0.8 mm.
The Φ50 large-size products are on ShiYi Automation's regular stock list. Standard lengths (500–3000 mm) are in stock for 1–3 day delivery. Special lengths and shaft-end machining are supported on request, with a 7–15 working day lead time.
Selection support — Tel / WhatsApp / WeChat: +86 189 0260 9613.
Spec values quoted from the TBI MOTION product catalog and converted to kN from the catalog's kgf ratings. Where a specific configuration differs, the model page governs.