Project Description
Introduction
The 9-Spline Internal Profile Seamless Steel Tube represents a precision-engineered evolution in tubular torque transmission design. It offers engineers a compelling middle ground between the coarse tooth pitch of an 8-spline and the finer engagement of a 10-spline configuration. The 9-tooth internal geometry is distinguished by its odd tooth count, a characteristic that delivers inherently smoother load cycling behavior.
Because no two diametrically opposite teeth are simultaneously in peak contact during rotation, this anti-phase loading property reduces vibration and noise in reciprocating drive systems. Each of the nine flanks shares the total circumferential load more evenly than an 8-spline at an equivalent pitch circle diameter. This yields a measurable reduction in peak contact stress per tooth while maintaining generous tooth root width for fatigue resistance.
Manufactured at Fushun Steel Tube via cold drawing over precision carbide mandrels, these seamless tubes benefit from continuous grain flow that follows every flank contour. Our process eliminates the microstructural discontinuities introduced by machining or broaching. For projects requiring alternative forming methods, explore our cold drawn steel tube capabilities. All 9-spline mandrel tooling is engineered to hold tooth form accuracy across the full drawn length, ensuring consistent involute or straight-sided geometry from end to end.
Product Overview & Geometry
Available in carbon, alloy, and bearing steel grades with full traceability and EN 10204 3.1 certification, Fushun Steel Tube's 9-spline precision tubing is production-ready for demanding drivetrain, hydraulic, and automation coupling applications. The odd-tooth configuration requires specialized metrology and tooling symmetry verification, which our engineering team manages in-house from prototype to volume production.
Contact our engineering team for a free 9-spline feasibility review and quotation tailored to your torque and environmental requirements.
Applications
The 9-spline internal profile occupies a strategically important position in the spline design spectrum. Its nine-tooth odd-count geometry creates an asymmetric tooth engagement pattern that inherently dampens torsional resonance. This makes 9-spline tubes especially valuable in high-cycle power transmission assemblies where harmonic vibration must be controlled without adding external damping components.
Primary Applications (Tubular Form)
- Agricultural machinery PTO coupling sleeves per ISO 500 and ASAE S205 standards for tractor and implement shaft connections.
- Off-highway and construction equipment final drive coupling tubes and wheel hub spline sleeves for high-shock environments.
- Marine propulsion shaft coupling bushings and sterndrive torque transfer sleeves utilizing 9-spline engagement for corrosive service.
- Industrial gearbox output shaft adapter tubes and speed reducer coupling sleeves for smooth, low-noise torque transfer.
- Hydraulic motor shaft connection sleeves and orbital motor torque tubes designed for positive, low-backlash engagement.
- Wind turbine yaw drive and pitch drive coupling tubes leveraging 9-spline geometry to minimize torsional oscillation.
- Precision servo actuator housings and collaborative robot joint transmission sleeves for extended maintenance intervals.
Supplementary Applications (Bar/Forging Form)
- Solid PTO drive shafts and implement input shaft stubs machined to external 9-spline profiles.
- Agricultural combine header drive shafts and harvester transmission components for standardized field serviceability.
- Heavy-duty pump drive hubs and compressor coupling flanges for quick-change shaft compatibility.
Need reliable torque transmission components for your next project?
Explore Cold Rolled Steel Tube OptionsSpecifications & Standards
The 9-spline seamless tube is manufactured in full conformance with internationally recognized precision tube production standards. Internal spline geometry is defined to applicable involute or straight-sided spline system specifications. The 9-tooth configuration is prominently codified in agricultural shaft standards, while industrial profiles are equally producible under general involute standards.
Seamless & Precision Tube Standards
- ASTM A519 Seamless carbon and alloy steel mechanical tubing
- EN 10305-1: Steel tubes for precision applications — seamless cold-drawn tubes
- DIN 2391 Seamless precision steel tubes (cold drawn)
- GB/T 3639: Cold-drawn or cold-rolled precision seamless steel tubes for mechanical structures
- GB/T 8162: Seamless steel tubes for structural purposes
Internal Spline Geometry Standards (9-Spline)
- ISO 500 / ASAE S205: PTO shaft spline standards covering 9-spline series for agricultural equipment.
- DIN 5480: Involute splines based on reference diameters — 9-tooth profiles producible to any module/pressure angle.
- ANSI B92.1 / SAE J498: Involute splines (US customary/metric) — 9-tooth series available per drawing specification.
- ISO 14: Straight-sided splines for cylindrical shafts — custom 9-tooth profiles produced to drawing.
- GB/T 3478 & GB/T 1144: Cylindrical involute and straight-sided splines per Chinese national standards.
Base materials comply with ASTM A29/A304, EN 10083-3, EN 10084, GB/T 3077, and JIS G4053. Mechanical and non-destructive testing follow ASTM E8/E23, EN ISO 6892-1, EN 10228-2, and GB/T 7735.
Available Sizes & Delivery
Fushun Steel Tube offers a broad manufacturing range for 9-spline precision tubing to serve both standardized PTO drivetrain applications and fully custom industrial coupling designs. All dimensional parameters are adjusted to match your technical drawing or referenced spline standard.
| Product Type | Outer Diameter (OD) | Wall Thickness (WT) | Length | Tolerance / Notes |
|---|---|---|---|---|
| Cold-Drawn 9-Spline Precision Tube | 20 mm – 180 mm | 3 mm – 25 mm | 2,000 – 6,000 mm | OD: IT7–IT9; Concentricity ≤ 0.05 mm TIR |
| Hot-Rolled Seamless Base Tube | 32 mm – 219 mm | 4 mm – 30 mm | 3,000 – 12,000 mm | As-rolled or pickled; for downstream machining |
| 9-Spline Internal Profile | Module 0.5 – 5.0 | Effective height per design | Splined length per drawing | Involute/straight-sided; Class 5–7 fit |
Delivery & Order Terms
- Ready Stock: Common OD/WT combinations in 42CrMo4/4140 and 20CrMnTi/8620 are maintained for priority dispatch. Typical lead time: ~7 days.
- Custom Specifications: Non-standard modules or alternative grades require an MOQ of 2–3 tons. Lead time: 25–35 days.
- Trial & Project Orders: Small-batch prototype tubes are accepted for engineering validation. Volume orders receive tiered pricing.
Chemical Composition
Grade selection for 9-spline tubing follows established metallurgical principles, with the added benefit that the nine-tooth count reduces peak contact stress per flank. This allows moderate relaxation of surface hardness requirements in some duty cycles while demanding high core toughness to resist tooth root fatigue.
| Grade | C | Si | Mn | Cr | Mo | Ni | Notes |
|---|---|---|---|---|---|---|---|
| 42CrMo4 / 4140 | 0.38–0.45 | 0.17–0.37 | 0.60–0.90 | 0.90–1.20 | 0.15–0.30 | ≤0.30 | Primary Q+T grade |
| 20CrMnTi / 8620 | 0.17–0.23 | 0.17–0.37 | 0.80–1.10 | 0.40–0.70 | 0.15–0.25 | 0.40–0.70 | Carburizing; Ti 0.04–0.10 |
| 35CrMo / 4135 | 0.32–0.40 | 0.17–0.37 | 0.40–0.70 | 0.80–1.10 | 0.15–0.25 | ≤0.30 | Medium-duty adapters |
| GCr15 / 52100 | 0.95–1.05 | 0.15–0.35 | 0.25–0.45 | 1.40–1.65 | ≤0.10 | ≤0.30 | High contact-stress sleeves |
Additional grades including 20CrNiMo, 16MnCr5, 30CrMnSiA, and boron-treated steels are available on request. Full composition limits are confirmed on the Mill Test Certificate.
Manufacturing Process
Production proceeds through a fully integrated process chain, from liquid steel to dimensionally verified finished tube. This ensures complete metallurgical traceability and tight geometric control of all nine internal tooth profiles.
Smelting & Refining
Standard production employs EAF + LF + VD processing for effective hydrogen removal and inclusion control. For high-cycle fatigue environments, ESR or PESR remelting significantly reduces non-metallic inclusion size. Consistent superheat control ensures carbon and alloy uniformity across every heat.
Tube & Spline Forming
The cycle begins with hot piercing and rolling of a seamless base shell, followed by spheroidizing annealing and phosphate-soap lubrication. The critical forming step is performed by cold drawing over a precisely ground carbide mandrel replicating the exact 9-tooth geometry. Because of the odd tooth count, mandrel geometry requires higher-order symmetry verification. The cold-drawing process compresses the bore plastically, generating a work-hardened surface layer and residual compressive stresses that enhance fatigue life. Multi-pass drawing with inter-pass annealing is applied for heavier walls. For complementary precision components, review our cold rolled steel tube manufacturing line.
Mechanical Properties
The mechanical performance envelope spans a wide range depending on grade, wall thickness, and heat treatment. The additional tooth reduces per-tooth torque share to approximately 11.1%, delivering a meaningful reduction in peak Hertzian contact pressure under reversed-torque conditions.
| Grade / Condition | Tensile (MPa) | Yield (MPa) | Elongation (%) | Hardness | Impact (J) @ RT |
|---|---|---|---|---|---|
| 42CrMo4 / Q+T | ≥ 1000 | ≥ 800 | ≥ 11 | 285–321 HBW | ≥ 50 |
| 42CrMo4 / As-Drawn + SR | 850–950 | 650–750 | 8–10 | 240–280 HBW | — |
| 35CrMo / Q+T | ≥ 930 | ≥ 780 | ≥ 12 | 265–310 HBW | ≥ 45 |
| 20CrMnTi / Normalized | ≥ 850 | ≥ 600 | ≥ 10 | 180–220 HBW | ≥ 40 |
| 20CrMnTi / Carburized | — | — | — | 58–62 HRC (case) | — |
| GCr15 / Spheroidized | 600–750 | 350–450 | ≥ 15 | 179–207 HBW | — |
| GCr15 / Q+T | ≥ 1600 | ≥ 1400 | ≥ 5 | 60–64 HRC | ≥ 15 |
Transverse Charpy V-notch values and low-temperature impact data are available upon request. Explicit impact test specification on the purchase order is recommended for shock-reversal applications.
Heat Treatment
Heat treatment follows fundamental metallurgical principles, with one notable nuance: the 40° angular tooth pitch makes case depth consistency sensitive to furnace atmosphere uniformity. Controlled-atmosphere or vacuum furnace processing is critical to prevent asymmetric hardness distribution.
| Treatment Type | Temperature Range | Cooling | Application / Remarks |
|---|---|---|---|
| Stress-Relief Annealing | 550–650 °C | Air cool | Relieves cold-drawing stresses; stabilizes dimensions |
| Normalizing (+N) | 850–900 °C | Air cool | Refines grain structure; prepares for carburizing |
| Quenching & Tempering | 830–860 °C / 500–650 °C | Oil/Water → Air | High core strength for 42CrMo4 and 35CrMo grades |
| Carburizing & Hardening | 900–930 °C / 820–850 °C | Oil → Temper | Hard wear-resistant case (0.8–1.5 mm) for 20CrMnTi |
| Spheroidizing Annealing | 780–810 °C | Furnace cool | Maximizes machinability for GCr15 bearing sleeves |
| Induction Hardening | Frequency per geometry | Polymer quench | Selective flank hardening without full furnace processing |
Atmosphere protection is strongly recommended for all cycles to preserve flank integrity and limit total decarburization depth across all nine tooth profiles.
Surface Finish & Tolerances
Dimensional and surface quality control accounts for the geometric complexity introduced by the odd nine-tooth arrangement. Since a nine-tooth profile cannot be verified by simple two-point diameter measurement, all bore inspections are performed using CMM three-point probing routines or dedicated 9-tooth spline gauges.
Cold-drawn tubes are supplied with a bright, phosphate-free bore surface finish of Ra ≤ 3.2 μm across all nine flanks. For high-speed servo or marine applications, we offer precision internal honing to Ra ≤ 1.6 μm. OD tolerances are held to IT7–IT9 as standard, with OD-to-pitch circle concentricity controlled within 0.02–0.05 mm TIR. External OD surfaces can be centerless ground to h6/h7 tolerances for bearing seats or press fits.
Quality Assurance & Testing
Fushun Steel Tube operates under an ISO 9001 certified quality management system with inspection procedures specifically adapted for odd-tooth internal spline profiles. Our metrology laboratory maintains certified 9-spline master gauges for functional verification across the full module range.
Inspection Workflow
- Raw Material: Optical emission spectrometry (OES) for chemical analysis; inclusion rating per ASTM E45.
- In-Process: Laser OD/WT gauging at each drawing pass; mandrel condition re-certification; wall eccentricity monitoring.
- Finished Tube NDT: Ultrasonic testing (UT) for internal flaws; Eddy Current (ET) or Magnetic Particle (MT) for surface defects.
- Mechanical & Metallography: Tensile, Charpy impact, hardness testing, grain size verification, and decarburization depth measurement.
- Geometry Verification: CMM three-point probing, dedicated go/no-go gauges, pitch circle runout, and tooth spacing uniformity checks.
All shipments include an EN 10204 Type 3.1 Mill Test Certificate. Type 3.2 certification with third-party witness testing is available. We support pre-shipment inspection by SGS, TÜV, BV, or client-appointed agencies.
Packing & Shipping
Finished tubes are individually protected with plastic end caps designed to fit the nine-tooth internal profile, preventing bore contamination and flank damage during transit. Each tube is wrapped in VCI anti-rust film or kraft paper and packed in fumigated wooden cases or reinforced steel crates. Hot-rolled base tubes are coated with water-soluble anti-rust oil and bundled with high-tensile steel strapping.
All packages carry comprehensive labeling including grade, heat number, dimensions, and full 9-spline specification data. Custom laser-etched heat/lot marking is available for traceability-critical projects. We support global ocean, air, and land freight with flexible container loading and documentation tailored to your import requirements or JIT delivery schedules.
Frequently Asked Questions
- Is 9-spline a recognized international standard, or is it only available as a custom profile?
- The 9-tooth internal spline has both standardized and custom dimensions. Agricultural PTO couplings reference 9-spline configurations per ISO and ASAE standards. Industrial profiles are fully definable under DIN 5480, ANSI B92.1, and GB/T standards by specifying nine teeth at the required module and pressure angle.
- What is the practical advantage of choosing 9-spline over 8-spline for torque transmission?
- The 9-spline reduces per-tooth contact stress by roughly 11% compared to an 8-spline. Its odd-tooth count creates anti-phase loading, meaning no diametrically opposite teeth peak simultaneously. This inherently dampens torsional micro-vibration and reduces gear whine in oscillating or reversing drive systems.
- Can Fushun Steel Tube produce 9-spline tubes for agricultural PTO shaft applications?
- Yes. PTO shaft 9-spline coupling sleeves are a core product line. We supply them in quench-and-tempered 42CrMo4/4140 or carburized 20CrMnTi/8620 conditions, meeting standardized PTO spline geometries for tractor implements, harvesters, and field machinery with direct assembly readiness.
- How do you verify 9-spline geometry given the odd tooth count prevents standard two-point measurement?
- We utilize CMM three-point probing routines programmed specifically for the 40° angular pitch. Dedicated 9-tooth functional go/no-go ring and plug gauges verify tooth thickness and fit class. Pitch uniformity and pitch circle concentricity to the OD are documented on every inspection record.
- What minimum order quantity and lead time apply for custom 9-spline precision tubes?
- Standard OD/WT combinations in 4140 or 8620 grades are stocked for ~7-day dispatch. Custom specifications require a 2–3 ton MOQ with a 25–35 day production lead time, covering mandrel preparation, cold drawing, heat treatment, and final metrology. Prototype batches are evaluated per project.
Ready to optimize your drivetrain with precision 9-spline tubing?
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