Custom Spline Shafts
Involute & Parallel Key

A spline shaft (also called a splined shaft) is a shaft with longitudinal teeth (splines) machined along its outer surface that mesh with matching internal splines (in a hub, sleeve, or coupling) to transmit torque while permitting axial sliding or precise angular positioning. Unlike a simple keyed shaft (one key, one keyway), a spline shaft distributes torque across multiple teeth, giving higher torque capacity, better concentricity, and lower stress concentration. Spline shafts are used wherever torque must be transmitted between a shaft and a sliding or fixed hub — automotive transmissions, robot joints, hydraulic pumps, and aerospace actuators.

Custom spline shaft pricing depends on six variables: (1) spline OD & module — larger and finer-pitch shafts cost more; (2) material — 20CrMnTi carburized steel is more expensive than 42CrMo4 induction-hardened; (3) accuracy class — DIN 5480 grade 5 (ground) is roughly 2× the price of grade 7 (hobbed only); (4) heat treatment — induction hardening + grinding adds 25–40%; (5) length and special features — long shafts, hollow shafts, and gear spline shafts cost more than simple short splines; (6) order quantity — prototypes cost more per unit than 100+ batches. Send your drawing for free customized spline shaft quotation — we respond within 48 hours with firm price, lead time, and spline shaft parts processing quotes.

Involute splines (covered by DIN 5480, ISO 4156, ANSI B92.1) have tooth profiles with an involute curve — the same profile geometry as gear teeth. This gives self-centering under load, high torque capacity, and the ability to be manufactured and inspected using the same equipment as gears. Parallel-key splines (DIN 5462/5463) have straight, flat-sided teeth with a rectangular cross-section — simpler to machine but lower load capacity and no self-centering. Involute splines are preferred for automotive and aerospace applications; parallel-key splines for lighter-duty machine tool and conveyor applications.

The four main standards are: DIN 5480 (German/European) — involute splines, metric module, 30° pressure angle, the dominant standard in European automotive and industrial applications. ISO 4156 — closely aligned with DIN 5480 but with some differences in fit class definitions; preferred for international procurement. ANSI B92.1 (imperial, diametral pitch) and ANSI B92.2M (metric) — American standards, widely used in North American automotive and hydraulic applications. SAE J498 for hydraulic pump couplings. HXC produces spline shafts to all four standards — specify your standard and fit class on the drawing.

The standard spline shaft manufacturing process for precision splines: (1) Blank turning — shaft OD, journals, and features machined to near-net shape with grinding stock. (2) Spline hobbing — involute spline teeth generated by CNC gear hobbing. (3) Heat treatment — induction hardening of spline zone or full carburizing, depending on application. (4) Spline tooth grinding — post-hardening profile grinding restores DIN 5480 grade 5–6 accuracy. (5) OD cylindrical grinding — bearing journals and datum diameters ground to final size. (6) Inspection — 100% go/no-go gauge and over-pin measurement.

Fretting is micro-slip wear at the spline tooth contact surface — a common failure mode in spline couplings subjected to cyclic torsional loads with vibration. It produces characteristic oxidized wear debris (fretting corrosion) and can progress to fretting fatigue cracking of the tooth root. Prevention methods: (1) Tight fit class — reduces relative micro-motion; (2) Surface hardening — hard tooth flanks resist micro-slip wear; (3) Lubrication — spline grease (MoS₂ or NLGI 2) in the coupling; (4) Increased tooth count — distributes load over more teeth; (5) Shot peening — compressive stress in the root resists crack initiation.

DIN 5480 defines spline fit by tolerance class and fit type. The shaft (external spline) is graded by tooth thickness tolerance (e.g., e, f, g for sliding fit; js for transition fit; k, n for press fit). The hub (internal spline) has a complementary grade. Common choices: Sliding fit (f/H) — for splines that must slide axially or be assembled with hand force; typical in transmissions and hydraulic pump couplings. Transition fit (js/JS) — for fixed couplings with some assembly tolerance. Press fit (k/K, n/N) — for permanent assemblies. Always specify both shaft and hub fit class on the drawing — mismatched classes are a frequent design error.

Spline shaft inspection uses three complementary methods: (1) Go/no-go spline gauges — the most practical method for production inspection. The "go" gauge (mating plug) verifies the total composite tolerance including tooth form, pitch, and concentricity in one functional check. The "no-go" gauge checks the tooth thickness is not too thin. (2) Over-pin (over-ball) measurement — two precision pins of known diameter placed in opposite tooth spaces and the span measured with a micrometer. Directly measures effective tooth thickness. (3) CMM with gear module — for precision-class splines requiring individual tooth profile, pitch, helix, and runout measurement per DIN 5480 or ISO 4156. HXC uses all three methods, with 100% go/no-go gauging and lot-sample CMM measurement.

A keyway shaft transmits torque through a single rectangular key fitting in a slot (keyway) machined in both shaft and hub. Simple, low-cost, but: high stress concentration at the keyway ends; poor concentricity (the hub can rock slightly on the key); limited torque capacity (only one contact surface). A spline shaft transmits torque through multiple teeth distributed around the circumference: much higher torque capacity per unit shaft diameter; excellent concentricity (self-centering involute profile); allows axial sliding without losing torque transmission; better fatigue life because stress is distributed. For applications above ~50 Nm or requiring high concentricity, spline shafts are significantly better than keyed shafts.

HXC's CNC spline shaft factory is located in Dongguan, Guangdong, China — a major precision manufacturing hub in the Pearl River Delta. We have been a Chinese spline shaft manufacturer since 2008, exporting to clients in Germany, USA, Japan, France, Italy, Korea, and 30+ other countries. All spline shaft machining, induction hardening, grinding, and CMM inspection are performed in-house at our China factory — no outsourcing. Factory visits and video audits are welcome for procurement teams qualifying new china cnc spline shaft suppliers.

Yes — hollow spline shafts are a HXC specialty. We machine hollow splined shafts from gun-drilled bar stock or seamless tube, with internal bores for weight reduction, oil / coolant passage, or cable routing. Common applications include robot joint shafts (saves ~40% mass vs solid), aerospace actuators, modern automotive driveshafts, and racing transmissions. Bore concentricity is held to ≤ 0.01 mm relative to the spline pitch circle. Send your hollow spline shaft drawing — we will review wall thickness, heat treatment distortion risk, and offer a customized quotation as part of our free DFM analysis.

Spline shaft material properties drive the application: 42CrMo4 (induction-hardened, HRC 52–58) is the standard for automotive transmission spline shafts and hydraulic pump spline shaft material steel — good fatigue resistance, predictable heat treatment, excellent machinability. 20CrMnTi (carburized, HRC 58–62) for maximum contact fatigue strength in high-torque drive shaft splines. SUS316L stainless for food, pharma, and marine. Al 7075-T6 (hard-anodized) for lightweight robot joint splines. Grade 5 titanium for aerospace. 17-4PH stainless for marine and defence. PEEK for medical sterilizable splines.

The most common pressure angles for involute spline shafts are: 30° (DIN 5480, ISO 4156) — the European metric standard; high pressure angle provides a wide tooth root, good load capacity, and self-centering. 37.5° and 45° — used in some ANSI B92.1 series for maximum root strength and minimal radial load on bearings. 20° — used in some fine-pitch splines where a larger number of thin teeth is preferred. The pressure angle affects tooth strength, self-centering stiffness, and the specific spline gauge required for inspection. Always specify the pressure angle explicitly — do not rely on the standard alone, as multiple PA options exist within each standard.

Standard parallel-axis spline shafts are designed primarily for torque transmission — they can transmit axial loads only if the spline is designed with an axial shoulder or retaining ring, as the tooth flanks themselves are not loaded axially in a standard involute spline coupling. For splines that must also transmit significant axial loads, a helical spline (similar to a helical gear profile) converts torque into an axial preload force — used in some aircraft engine accessory drives. For light axial loads (preload only), a sliding fit spline with a retaining snap ring on the shaft end is the simplest solution. HXC designs spline shafts for combined torque and axial load if required — include your load requirements in the drawing notes.

Spline shaft torque capacity depends on spline OD, module, tooth count, face width, and material hardness. As a rough guide: a DIN 5480 involute spline shaft with m1.5 / 30T / Ø45mm in 42CrMo4 (induction hardened) can transmit approximately 500–800 Nm continuously. Capacity scales roughly with the cube of the spline OD for the same module. Key design limits: tooth shear stress (root shear), contact stress (flank Hertzian pressure), and fretting fatigue at the tooth root. HXC engineers can calculate spline torque capacity and recommend module/tooth count for your application as part of the free DFM review.

Lubrication depends on the coupling type: Fixed spline couplings (no axial sliding in service): a one-time application of molybdenum disulfide (MoS₂) grease or anti-seize compound at assembly is sufficient. Sliding spline couplings (spline slides axially during operation, e.g., driveshaft slip yokes): require a spline-specific grease (NLGI 2 lithium complex with MoS₂ or graphite) replenished per maintenance schedule. Oil-bath environments (gearbox internals): lubricated by the transmission oil — ensure the oil type is compatible with spline material (EP additives needed for steel splines). Stainless and titanium splines are more tolerant of dry running but still benefit from lubrication.

DIN 5480 accuracy grades: Grade 8–9 — hobbed only, no grinding; adequate for slow-speed, low-load industrial spline couplings and large agricultural equipment. Grade 7 — hobbed and lightly deburred; general industrial and automotive non-critical applications. Grade 6 — hobbed + ground; standard for automotive transmissions, hydraulic pump splines, and robot joint drives. Grade 5 — precision ground; for servo robot joints, aerospace actuators, and precision instrument drives where backlash must be tightly controlled. Each step down in grade roughly doubles the inspection and manufacturing cost. Our engineers will recommend the correct grade based on your torque, speed, and positional accuracy requirements.

Lead times for spline shafts: Prototype (1–5 pcs), 5-axis milled: 5–8 days. Small batch (10–50 pcs), hobbed + ground, DIN 5480 grade 6: 8–14 days. Production batch (100–2,000 pcs), hobbed + hardened + ground: 12–18 days. Stainless or titanium spline shafts: add 3–5 days for passivation or additional machining difficulty. Long shafts (>500mm): add 2–3 days for straightness correction after heat treatment. Rush production is available — discuss your timeline when uploading your drawing.

Yes — we regularly manufacture gear spline shafts that combine external splines, external gear teeth, bearing journals, threaded ends, and mounting flanges in a single shaft. All features are produced in a sequenced operation set ensuring concentricity between the spline, gear, and bearing seats. Examples include: automotive transmission shafts with involute splines at one end and helical gear teeth in the middle; robot joint shafts with splines and integrated bevel gear; hydraulic motor shafts with splines and flange mounting. These are the most complex precision shafts we make — and the most common custom request. Send us your drawing for a free DFM review and quotation.