Star Elastic Coupling – ROTEX® Replacement, 20CrMo Steel, 98ShA Spider, 6.3–1120 N·m

Factory direct | 20CrMo alloy steel hubs | 98ShA polyurethane star spider | 6.3–1120 N·m torque | 0–10000 RPM | Axial plug-in installation | Maintenance-free | Interchangeable with ROTEX® | OEM/ODM/OBM

The Apexcoupling DJ-A series is a high-performance star elastic coupling (curved jaw / spider type) designed for reliable power transmission in demanding industrial applications. Featuring 20CrMo alloy steel hubs and a 98ShA polyurethane star spider, this coupling delivers excellent shock absorption, vibration damping, and misalignment compensation. The star-shaped elastomer design provides cushioning, wear resistance, and maintenance-free operation across a wide temperature range of -35°C to +80°C. With compact dimensions, low inertia, and axial plug-in installation, the DJ-A series is the ideal replacement for ROTEX® couplings – offering the same performance at factory-direct pricing. Suitable for servo motors, stepper motors, conveyors, pumps, compressors, and general industrial machinery.

✅ Direct replacement for ROTEX® series – same dimensions, same performance, better value. 98ShA polyurethane spider – cushioning, vibration reduction, wear resistance. Maintenance-free – no lubrication required.

Key Technical Specifications

🔧 Custom bores, keyways, spider hardness (92ShA, 95ShA, 98ShA, 64ShD), and special materials available. Contact us with your specifications.

DJ-A Series – Model Range (Reference)

📐 Additional sizes available. Contact us for complete dimensional data and custom sizing.

Product Structure

1. Two 20CrMo Steel Hubs – High-strength chromium-molybdenum alloy steel, precision-machined with curved jaws, keyway + set screw fastening.

2. 98ShA Polyurethane Star Spider – Star-shaped elastomer insert that transmits torque, absorbs shock, dampens vibration, and compensates for misalignment.

3. Axial Plug-in Design – Allows for easy installation and removal without moving connected shafts.

💡 How it works: The DJ-A star elastic coupling consists of two hubs with curved jaws and a central star-shaped polyurethane spider. Power is transmitted through the spider, which flexes to accommodate angular, parallel, and axial misalignment while absorbing shock and vibration. The 98ShA hardness provides high torsional rigidity while still offering excellent damping characteristics. The star-shaped design with convex claw blocks prevents internal deformation from impact and external deformation from centrifugal force .

Product Features & Advantages

Why Choose 20CrMo Steel?

20CrMo is a chromium-molybdenum alloy steel with excellent mechanical properties:

• High tensile strength – 590–750 MPa 

• Good yield strength – 355–440 MPa 

• Excellent toughness – Performs well under high stress and impact loads 

• Good hardenability – Can be heat-treated for high hardness 

• Wear resistance – Suitable for high-cycle industrial applications 

✅ 20CrMo is the material of choice for high-performance industrial couplings requiring strength, durability, and reliability.

98ShA Spider – The Heart of the Coupling

The 98ShA polyurethane spider is the critical component that determines coupling performance:

💡 The 98ShA hardness is the standard rating for nominal torque in the DJ-A series . For higher torque applications, consider 64ShD (higher stiffness); for higher damping, consider 92ShA or 95ShA.

DJ-A vs ROTEX® – Direct Replacement

✅ The DJ-A series is a direct replacement for ROTEX® couplings – offering the same performance, same dimensions, and better value .

Applications

• Servo Motors – High-precision motion control, zero backlash requirement

• Stepper Motors – Accurate positioning, no lost motion

• Conveyors – Material handling systems

• Pumps – Centrifugal, gear, and diaphragm pumps

• Compressors – Air and gas compressors

• Fans & Blowers – Ventilation systems

• Mixers – Industrial mixing equipment

• Printing Equipment – Register control, high-speed operation

• Packaging Machinery – Wrapping and sealing machines

• Machine Tools – Spindle drives, positioning systems

• Textile Machinery – Spinning, weaving equipment

• Food & Beverage Processing – Hygienic, reliable drives

Why Choose Apex Coupling for DJ-A Star Couplings?

FAQ

Q: What is a star elastic coupling?
A: A star elastic coupling (also called a jaw coupling, spider coupling, or curved jaw coupling) consists of two metal hubs with curved jaws and a central star-shaped elastomer spider. It transmits torque while absorbing shock, dampening vibration, and compensating for misalignment .

Q: Is the DJ-A series a direct replacement for ROTEX® couplings?
A: Yes. The DJ-A series is fully interchangeable with KTR ROTEX® series couplings – same dimensions, same performance, better value .

Q: What materials are used?
A: The hubs are made of 20CrMo alloy steel – offering high strength, toughness, and wear resistance . The spider is made of 98ShA polyurethane – providing excellent damping, wear resistance, and temperature stability .

Q: What is the 98ShA spider hardness?
A: 98ShA refers to the Shore A hardness of the polyurethane spider. 98 Shore A provides high torsional rigidity while still offering excellent vibration damping. It is the standard hardness for nominal torque in the DJ-A series .

Q: What is the torque and speed range?
A: Allowable torque range is 6.3–1120 N·m and maximum speed is 10000 RPM. Specific ratings vary by model size.

Q: Does the coupling have backlash?
A: The DJ-A series features zero backlash with preloaded spider – no rotational clearance, ensuring precise positioning for servo and stepper motors.

Q: Does the coupling require lubrication?
A: No. The DJ-A series is maintenance-free – no lubrication required .

Q: What is the operating temperature range?
A: The working temperature range is -35°C to +80°C .

Q: How is the coupling installed?
A: The DJ-A series features axial plug-in installation – simply slide the spider between the two hubs. No special tools required .

Q: Can I get a custom coupling?
A: Yes. We offer OEM, ODM, and OBM support – custom bores, keyways, spider hardness, and materials available.

Request a Quote

Send us your model size (e.g., DJ24A, DJ38A), bore size, torque, speed, and application details. Our engineers will recommend the optimal model and provide a quotation within 24 hours.