The SL Type Oldham Coupling connects coaxial drive shafts with large radial offset compensation — up to 8.0 mm across 18 sizes (SL70–SL460). Nominal torque 120–63,000 N·m, speed 70–250 r/min. Aluminium alloy or stainless steel hub options. Zero backlash, constant velocity ratio. Stocked and shipped globally by RP.
An Oldham coupling is a three-piece mechanical coupling designed to transmit rotary motion between two parallel shafts that are not perfectly aligned. The assembly consists of two metallic hubs — each keyed or clamped to one of the rotating shafts — and a central intermediate disc (also called a slider or middle element) that slides within mating slots machined into each hub face. This sliding cross arrangement allows the centre element to move laterally as the shafts rotate, absorbing radial (parallel) misalignment without generating side-loads on the connected shaft bearings.
The fundamental engineering problem the Oldham design addresses is this: in real machinery, perfect shaft colinearity is rarely achievable. Motor mounting tolerances, thermal expansion, foundation settling, and general assembly variation all introduce some degree of parallel offset between coupled shafts. A rigid coupling transmits these offsets directly to bearings, seals, and shaft spigots, accelerating wear and ultimately causing premature failure. An Oldham coupling intercepts that offset at the floating intermediate disc, keeping the force path clean and the bearing loads predictable.
What distinguishes the Oldham design from elastomeric couplings — such as jaw or tyre-type units — is its essentially rigid, zero-backlash torque path. There is no rubber element to fatigue, creep, or change stiffness with temperature. The intermediate disc material (nylon, Delrin/POM, or similar engineering polymer) handles the sliding function without transmitting cyclic bending moments. This makes the Oldham coupling the preferred choice wherever constant velocity ratio, minimal torsional compliance, and long service life under parallel offset are all required simultaneously.
The three-piece structure operates on a straightforward kinematic principle. Each hub face carries a single rectangular tongue, and the intermediate disc carries two perpendicular slots — one on each face — that receive these tongues. As the drive hub rotates, its tongue pushes the disc in one linear direction; the disc simultaneously slides in a perpendicular direction relative to the driven hub. The net result is pure torque transfer with the centre of mass of the disc describing a small circular orbit equal in diameter to the radial offset between the shafts. Critically, the angular velocity ratio between input and output remains exactly 1:1 throughout each revolution — this is the constant-velocity (CV) characteristic that defines the Oldham mechanism.
For the SL series, the allowable radial compensation ranges from 0.6 mm on the SL70 up to 8.0 mm on the SL460. Angular misalignment tolerance is 0.5° across the full range. Axial (end-float) compensation varies from 1.2 mm (SL70) to 7.2 mm (SL460), providing flexibility for thermal shaft growth in long spindle applications. Rated torques span from 120 N·m to 63,000 N·m, and allowable speeds range from 70 r/min (SL460) to 250 r/min (SL70 through SL320).
Because the intermediate disc carries the misalignment kinematically rather than elastically, the torsional stiffness of the coupling is high. There is no energy stored in elastic deformation and no phase lag between input and output torque. This characteristic is particularly significant in servo-driven positioning systems, where any elastic windup would appear as a tracking error. The low rotational inertia of the SL series — as low as 0.002 kg·m² on the SL70 — also minimises the reflected inertia presented to servo drives, enabling faster dynamic response and tighter control bandwidths.
The tables below list all published performance parameters and dimensional data for the SL series. Use these for initial selection; our engineering team can assist with final confirmation based on your application duty cycle and installation envelope.
| Type | Nominal Torque Tn (N·m) | Allowable Speed [n] (r/min) | Bore Dia. d (mm) | D (mm) | D1 (mm) | L (mm) | H (mm) | S (mm) | Rotational Inertia (kg·m²) | Weight (kg) |
|---|---|---|---|---|---|---|---|---|---|---|
| SL70 | 120 | 250 | 15–18 | 70 | 32 | 42 | 14 | 0.5 | 0.002 | 1.5 |
| SL90 | 250 | 250 | 20–30 | 90 | 45 | 52 | 14 | 0.008 | 2.6 | |
| SL100 | 500 | 250 | 36–40 | 110 | 60 | 70 | 19 | 0.026 | 5.5 | |
| SL130 | 800 | 250 | 45–50 | 130 | 80 | 90 | 19 | 0.07 | 10 | |
| SL150 | 1250 | 250 | 55–60 | 150 | 95 | 112 | 19 | 0.14 | 15.5 | |
| SL170 | 2000 | 250 | 65–70 | 170 | 105 | 125 | 24 | 0.25 | 22.4 | |
| SL190 | 3200 | 250 | 75–80 | 190 | 110 | 140 | 29 | 0.5 | 31.5 | |
| SL210 | 5000 | 250 | 85–90 | 210 | 130 | 160 | 33 | 0.9 | 45 | |
| SL240 | 8000 | 250 | 95–100 | 240 | 140 | 180 | 33 | 1.6 | 59.5 | |
| SL260 | 9000 | 250 | 100–110 | 260 | 160 | 190 | 33 | 2 | 76 | |
| SL280 | 10000 | 100 | 110–120 | 280 | 170 | 200 | 33 | 3 | 94.3 | |
| SL300 | 13000 | 100 | 120–130 | 300 | 180 | 210 | 43 | 1.0 | 4.3 | 111 |
| SL320 | 16000 | 100 | 130–140 | 320 | 190 | 220 | 43 | 5.7 | 129 | |
| SL340 | 20000 | 100 | 150 | 340 | 210 | 250 | 48 | 8.4 | 162 | |
| SL360 | 32500 | 100 | 160 | 360 | 240 | 280 | 48 | 19.2 | 258 | |
| SL400 | 38700 | 80 | 170 | 400 | 260 | 300 | 48 | 26.1 | 305 | |
| SL460 | 63000 | 70 | 200 | 460 | 300 | 350 | 58 | 62.9 | 560 |
| Type | Radial Offset delta y (mm) | Angular Offset delta a (°) | Axial Offset delta x (mm) |
|---|---|---|---|
| SL70 | 0.6 | 0.5° | 1.2 |
| SL90 | 0.7 | 1.4 | |
| SL100 | 1.4 | 1.5 | |
| SL130 | 1.8 | 1.8 | |
| SL150 | 2.2 | 2.0 | |
| SL170 | 2.6 | 2.1 | |
| SL190 | 3.0 | 2.2 | |
| SL210 | 3.4 | 2.6 | |
| SL240 | 3.8 | 3.0 | |
| SL260 | 4.0 | 3.4 | |
| SL280 | 4.4 | 3.8 | |
| SL300 | 4.8 | 4.2 | |
| SL320 | 5.2 | 4.6 | |
| SL340 | 6.0 | 5.0 | |
| SL360 | 6.4 | 5.7 | |
| SL400 | 6.6 | 6.4 | |
| SL460 | 8.0 | 7.2 |
Lightweight and electrically insulating. Ideal for high-speed lighter-duty applications where cost and mass are priorities. Self-lubricating properties reduce wear between sliding faces.
Higher rigidity and superior wear resistance compared to nylon. Suitable for heavier torque loads and applications where dimensional stability under load is critical. Low moisture absorption maintains consistent clearance over time.
The standard choice for most industrial applications. Excellent strength-to-weight ratio, good machinability for custom bores and keyways, and natural resistance to many industrial environments. Anodising or hard-coat options available.
Specified for food processing, pharmaceutical, marine, and other corrosive environments. Withstands washdown procedures and aggressive cleaning agents. Grade 304 and 316 options available on request.
Selecting the right coupling type starts with matching the compensation requirement and application duty to the coupling's inherent characteristics.
| Parameter | SL Oldham Coupling | Jaw Coupling | Bellows Coupling | Disc Coupling |
|---|---|---|---|---|
| Parallel Offset Compensation | Excellent (up to 8 mm) | Limited (0.1–0.5 mm) | Low (0.1–0.3 mm) | Very Low (<0.1 mm) |
| Angular Offset Compensation | Low (0.5°) | Moderate (1°–2°) | Good (1°–3°) | Low (0.5°–1°) |
| Backlash | Near Zero | Low–Moderate | Near Zero | Near Zero |
| Electrical Insulation | Yes (polymer disc) | Yes (spider) | No | No |
| Suitable Speed Range | 70–250 r/min | Up to 6000 r/min | Up to 10,000+ r/min | Up to 10,000+ r/min |
| Installation & Maintenance | Simple — disc slides out radially | Simple — spider accessible | Moderate | More complex |
| Relative Cost | Moderate | Low | High | High |
| Constant Velocity Ratio | Yes — true 1:1 CV | Yes | Yes | Yes |
Choosing the right supplier is as important as choosing the right coupling. Our quality system, technical depth, and ability to support custom requirements help keep projects on schedule and on budget.
Our SL Type Oldham Couplings are manufactured under an ISO 9001 quality management system. Products comply with RoHS directives and are supplied with CE conformity documentation on request. Material test certificates (MTC) for steel and stainless steel hubs are available for critical applications.
We support custom bore diameters, keyway profiles (parallel, Woodruff, DIN, and standard), special hub materials, surface treatments (hard anodising, electroless nickel plating, black oxide), and modified intermediate disc materials. Minimum order quantity for custom specifications is 5 pieces, with typical lead times of 7–15 business days from drawing approval.
Ready to discuss your application? Our team is equipped to assist with selection, sizing, and custom specification. Get in touch with a RP coupling specialist today.
Send us your shaft diameter, torque requirement, and speed, and our engineering team will verify the correct SL size and material specification — usually within one business day.
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