PTO Shaft → PTO Shaft for Discbines → S Series
S Series PTO Shaft — Star Tube S6 to S50
for Discbines, Balers & Heavy Agricultural Implements
11 star-profile series from S6 to S50, covering the full torque range demanded by modern pull-type and 3-point discbines. Induction-hardened cross kits, friction clutch overload protection, full CE-compliant safety shield, and OEM configuration on request.
✔ CE Certified
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✔ Star-Profile Spline Tube
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✔ 540 & 1000 RPM Compatible
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✔ Friction Clutch Standard
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✔ OEM / Custom Lengths Available
What Is the HZPT S Series PTO Shaft?
The S Series PTO shaft is a star-profile (also known as “S-profile” or “star tube”) telescoping driveline designed to transmit rotational power from a tractor’s Power Take-Off output to heavy agricultural implements — discbines, round balers, square balers, flail mowers, manure spreaders, and high-torque tillage equipment.
Unlike the round-bore G Series, the S Series uses a multi-lobe star cross-section on both the inner and outer spline tubes. This profile geometry distributes torque loads across a larger contact surface, reducing peak contact stress per lobe compared to equivalent round-spline designs. The result: higher torque capacity per unit of tube diameter and reduced fretting wear during repeated extension-compression cycles.
HZPT manufactures 11 S Series grades — S6, S7, S8, S9, S10, S32, S36, S38, S42, S48, and S50 — each matched to a specific cross kit size, yoke bore, and tube wall thickness. The S50, at the top of the range, is engineered for implements exceeding 100 kW PTO input at 540 RPM, making it a direct competitor to OEM drivelines on high-horsepower European tractors.
Each shaft ships with a full-coverage polypropylene safety shield, a grease-purge-capable cross kit, and a pre-set friction clutch. All configurations are CE marked per Machinery Directive 2006/42/EC.
S Series PTO Shaft — Component Reference Table
Use this table to identify cross kit part numbers, joint assembly codes, splined yoke references, and tube outer/inner profile codes for each S Series grade. Cross kit dimensions are listed as trunnion diameter × cup OD (mm). Use column numbers (1–8) to locate the correct part when ordering replacements.
| Series | Cross Kit
(col 1) | Joint Assembly Code | Splined Yoke
(col 4) | Tube Yoke | Tube Profile |
|---|
Outer
(col 2) | Inner
(col 3) | Outer
(col 5) | Inner
(col 6) | Outer
(col 7) | Inner
(col 8) |
|---|
| G2 | 2.01
(23.8 × 61.3) | 2.0505B + 2.01 + 2.06G | 2.0505B + 2.01 + 2.07G | 2.0505B | 2.06G | 2.07G | 50 × 2.5 | G35-18 |
| G4 | 4.01
(27 × 74.6) | 4.0505B + 4.01 + 4.06G | 4.0505B + 4.01 + 4.07G | 3.0505B | 4.06G | 4.07G | 50 × 2.5 | G35-18 |
| G5 | 5.01
(30.2 × 80) | 5.0505B + 5.01 + 5.06G | 5.0505B + 5.01 + 5.07G | 5.0505B | 5.06G | 5.07G | 60 × 3 | G40-14 |
| G6 | 6.01
(30.2 × 92) | 6.0505B + 6.01 + 6.06G | 6.0505B + 6.01 + 6.07G | 6.0505B | 6.06G | 6.07G |
| G7 | 7.01
(30.2 × 106.5) | 7.0505B + 7.01 + 7.06G | 7.0505B + 7.01 + 7.07G | 7.0505B | 7.06G | 7.07G |
| G8 | 8.01
(35 × 106.5) | 8.0505B + 8.01 + 8.06G | 8.0505B + 8.01 + 8.07G | 8.0505B | 8.06G | 8.07G | 65 × 3.5 | G45-16 |
| G38 | 38.01
(38 × 105.6) | 38.0505B + 38.01 + 38.06G | 38.0505B + 38.01 + 38.07G | 38.0505B | 38.06G | 38.07G |
| G42 | 2600
(42 × 104.5) | 42.0505B + 42.01 + 42.06G | 42.0505B + 42.01 + 42.07G | 42.0505B | 42.06G | 42.07G | 75 × 4 | G55-20 |
| G50 | 50.01
(50 × 118) | 50.0505B + 50.01 + 50.06G | 50.0505B + 50.01 + 50.07G | 50.0505B | 50.06G | 50.07G |
* Cross kit dimensions shown as trunnion Ø × cup OD (mm). Column numbers (1–8) correspond to part position in the standard assembly diagram. Contact HZPT with your series designation and column number when ordering individual replacement components.
⚠ Note on S vs G Series numbering: The S Series component codes listed above follow HZPT’s internal G-prefix joint system (e.g., G35-18 inner tube) — this refers to the joint standard, not the shaft series. An S6 shaft uses a G40-14 inner tube but is classified as an S Series driveline based on its star-profile spline geometry. Specify “S Series” when ordering to ensure the correct tube profile is supplied.
6 Engineering Advantages of the S Series Star-Profile PTO Shaft
Star-Profile Torque Distribution
The multi-lobe star cross-section spreads rotational load across more contact surface than a round or square bore. At equivalent outer diameter, the S Series star tube transmits higher torque without increasing tube wall thickness — critical for weight-sensitive implement designs where driveline mass affects field handling.
Reduced Fretting Wear on Telescoping
The S-profile’s multiple contact lobes maintain consistent radial stiffness throughout the stroke range. This prevents the rocking motion (micro-rotation under load) seen in round-spline tubes that causes accelerated fretting at tube overlap points. Field result: longer tube service life between replacement intervals.
Induction-Hardened Cross Kit Journals
Trunnion journals are induction-hardened to 58–62 HRC for extended bearing needle roller life under continuous oscillation. Each cross kit includes a grease nipple on all four trunnion caps for on-machine lubrication without disassembly. Recommended interval: every 8 hours under full-load operation.
Calibrated Friction Clutch Overload
Integrated friction clutch slips at a factory-set torque threshold, protecting both the tractor gearbox and the implement input shaft from shock loads caused by rock strikes, slug feeding, or sudden stall. Calibration is series-matched — the S50 clutch, for example, is set for peak torque levels appropriate to 100 kW+ PTO outputs.
CE-Compliant Full-Coverage Safety Shield
The non-rotating polypropylene shield covers the full shaft assembly from tractor-end yoke to implement-end yoke. Shield retention cones are reinforced to resist contact with crop residue, loose soil, and low-clearance ground contours. Compliant with EU Machinery Directive 2006/42/EC and OSHA 1928.57 requirements.
11 Grades — One Supplier
From S6 (compact, light-duty) through S50 (heavy, 100 kW+), HZPT covers the full S Series range from a single manufacturing facility. That means consistent cross-kit standards, compatible yoke bores across adjacent series, and a single point of contact for spare parts — no juggling multiple vendors for a mixed implement fleet.
How to Attach an S Series PTO Shaft to a Tractor — 6-Step Procedure
Incorrect attachment is the leading cause of PTO shaft failure and the most common source of PTO-related injury. Follow this sequence every time:
1
Park & Align — Engine Off, PTO Disengaged
Position the tractor on level ground with the implement directly behind it. Engage the tractor park brake and shut the engine off completely — never attach a PTO shaft with the engine running. Rotate the implement input shaft by hand until it aligns with the tractor’s PTO stub shaft.
2
Slide the Tractor-End Yoke onto the PTO Stub
Lift the S Series shaft and slide the tractor-end splined yoke over the PTO stub shaft. Rotate the yoke slowly until the splines engage — you’ll feel them drop into alignment. Push fully inward until the quick-release collar clicks audibly into the stub shaft groove. Tug back to confirm the locking mechanism is seated.
3
Secure the Locking Pin or Snap Collar
If the tractor-end yoke uses a bolt-type retention (common on older tractors), install and torque the retaining bolt to the tractor manufacturer’s specification — typically 25–40 Nm for 1-3/8″ stubs. For quick-release collar designs, verify the collar spring is fully extended and the collar is seated behind the stub shaft groove, not on top of it.
4
Attach the Implement-End Yoke
Extend the S Series telescoping shaft to reach the implement input shaft. Slide the implement-end yoke onto the input splines, rotating until engaged and locked. Check that the yoke locking mechanism — snap ring, clip pin, or bolt — is fully secured. The implement end must be as secure as the tractor end; a loose implement-end yoke is as dangerous as a loose tractor-end one.
5
Attach the Safety Shield Retaining Chains
The S Series safety shield must be anchored to a fixed point on both the tractor and implement — not to the rotating shaft. Use the included retaining chains or straps, connecting them to the tractor drawbar bracket and the implement frame. The chains prevent the shield from rotating with the shaft if the shield bearing fails. A rotating shield is as dangerous as no shield.
6
Low-Speed Function Check Before Field Entry
With all personnel clear of the shaft, start the tractor, engage the PTO at low RPM (approx. 200–300 RPM), and observe the shaft for 10–15 seconds. Confirm: no vibration, no unusual noise, shield not rotating, and no visible wobble at the yoke joints. Only after this check is complete should you increase to operating RPM and proceed to the field.
⚠ Critical length check: Before operating, move the tractor through its full turning range and verify the PTO shaft does not fully compress (inner tube bottoms out) or reach its minimum overlap at any point. Minimum recommended spline overlap for S Series tubes: 150 mm at full extension. Bottoming out under load can crack the tube yoke; running at minimum overlap can cause the shaft to pull apart mid-field.
Where the S Series PTO Shaft Is Used
The S Series star-tube design is particularly well-suited to applications where torque density matters and driveline mass is a constraint:
🌾
Discbines & Mower-Conditioners
S7–S9 typical. High-speed disc blade drives demand consistent torque transfer with zero shaft play — star profile delivers this across the full stroke range.
🌀
Large Square & Round Balers
S8–S42. Cyclic shock loads from knotter mechanisms and crop slug ingestion are handled by the calibrated friction clutch without interrupting baling rhythm.
🪵
Industrial Wood Chippers
S42–S50. Large-diameter infeed creates extreme instantaneous torque spikes; the S50 is sized for 100 kW+ PTO outputs with peak torque events above 3,500 Nm.
🚜
Rotary Tillers & Power Harrows
S6–S8. Continuous full-load operation in high-vibration soil engagement conditions; star profile minimizes micro-slip at tube overlap under sustained torque.
♻️
High-Capacity Manure Spreaders
S9–S36. Frozen or compacted loads create start-up torque spikes 3–4× the running load; friction clutch absorbs these without damaging the beater shaft.
🏗
OEM Implement Manufacturing
HZPT supplies S Series drivelines as OEM-specified components to implement manufacturers in Europe, North America, and Australia. Custom yoke bores and lengths available at MOQ 50+ units.
Frequently Asked Questions — S Series PTO Shaft
What is the difference between the S Series star tube and the G Series spline tube?
＋
The fundamental difference is the cross-sectional profile of the telescoping tubes. The G Series uses a round-spline (involute) profile — teeth around the circumference of a circular bore — which provides good torque capacity but allows slight radial play under load reversals. The S Series uses a star (multi-lobe) profile that distributes torque across lobes with larger contact areas per lobe, reducing contact stress and micro-slip during telescoping under load. In practical terms: the S Series is preferred for applications with continuous load at varying shaft angles (discbines, mower-conditioners), while the G Series is often selected for steady-state, fixed-angle applications (pumps, augers). Both series are available with identical cross kit and yoke standards — the only non-interchangeable component is the tube profile itself.
Can I replace just the inner or outer tube on my S Series shaft without replacing the whole assembly?
＋
Yes. HZPT supplies S Series inner tubes (col 8) and outer tubes (col 7) as separate line items, identified by the part codes in the component table above. When ordering replacement tubes, specify: (1) the S Series grade, (2) whether you need the inner or outer tube, and (3) your required length. Note that inner and outer tubes are matched pairs within a series — mixing an S8 inner tube with an S7 outer tube will result in either excessive clearance or an interference fit. Always replace both tubes if the bore or OD shows visible wear channels deeper than 0.3 mm.
How do I know if my S Series friction clutch needs adjustment or replacement?
＋
Three signs indicate a friction clutch that needs attention: (1) Slipping under normal operating load — if the clutch slips when the implement is running at rated speed and load without any slug or obstruction, the clutch disc is worn below minimum thickness or the spring preload has relaxed. (2) Not slipping during a genuine overload event — if a rock strike or slug stall causes a loud bang and the implement stalls rather than the clutch slipping, the disc is either seized or the friction surfaces are glazed. (3) Chattering or rattling at low RPM — worn friction discs can generate a characteristic chatter at idle-speed PTO engagement. HZPT supplies replacement friction disc kits for each S Series grade; the spring pack is not field-adjustable and must be replaced as a unit if preload is lost.
Does HZPT supply S Series PTO shafts for European implement brands (e.g., Kuhn, Krone, Claas)?
＋
Yes. Many European discbine and mower-conditioner manufacturers specify S Series star-profile drivelines as OEM equipment, and HZPT manufactures to these specifications. For aftermarket replacement applications, provide the brand, model, and the five key measurements (overall length, cross kit size, inner/outer tube diameter, and spline count) so we can confirm cross-compatibility. Note that some Kuhn and Krone implements use proprietary yoke bore dimensions that require a custom yoke — HZPT can supply custom yoke bores at MOQ 25 units. Contact our technical team with your implement model number for a direct compatibility check.
What is the correct grease type and interval for S Series cross kits?
＋
Use NLGI #2 lithium-complex grease or equivalent EP2 grease rated for operating temperatures of −20°C to +120°C. Apply via the grease nipple on each trunnion cap until fresh grease purges from the bearing seal — this confirms the needle roller cavity is fully charged. Purge-grease every 8 operating hours under full-load field conditions, or at the start of each season if the implement is stored over winter. Avoid petroleum-based greases with no EP (Extreme Pressure) additives — under shock loading the needle rollers can break through the lubricant film, causing brinelling of the trunnion journal within 20–30 hours. Replace the cross kit if journal spalling or pitting is visible on inspection.
What Operators Say About the S Series PTO Shaft
★★★★★
“My neighbor told me to just get a standard PTO shaft, said the star tube stuff was overkill for hay. That same neighbor had to quit baling at noon last August because his shaft sheared clean through on a wet mat of orchard grass. I kept going until 9 PM. Now he asks me where I bought mine. I told him HZPT S9 — he wrote it down on his hand with a marker. I consider that a five-star review from two farms.”
CT
C. Tanner
Hay & Forage Farmer — Willamette Valley, Oregon, USA
Verified Purchase · S9 × 2 units
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OEM & wholesale inquiries welcome · Custom lengths & yoke bores available · Ships worldwide
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