Double star elastic couplings (also known as double spider couplings) are essential for applications requiring superior misalignment compensation and zero-backlash torque transmission. The DJ-S series from Apex Coupling features a dual elastomer design that provides exceptional compensation for angular, radial, and axial deviations.

This guide explains how double star elastic couplings work, their key advantages, and how to select the right model for your application.

1. What Is a Double Star Elastic Coupling?

A double star elastic coupling consists of:

• Two hubs – precision-machined from 45# steel or aluminum alloy

• Two star-shaped polyurethane elastomers –串联 for superior misalignment compensation

The dual elastomer design allows the coupling to compensate for large installation deviations, damping vibration and reducing noise. The polyurethane elastomers provide zero backlash operation, maintenance-free performance, and excellent shock absorption.

💡 Double star elastic couplings are ideal for applications requiring high misalignment compensation, such as machine tool spindles, lifting platforms, and long-span drives.

2. Single Star vs Double Star – Why Choose Double?

✅ Choose double star (DJ-S) when: Your application has large installation deviations, requires superior vibration damping, or involves long-span drives.

3. Key Advantages of DJ-S Double Star Couplings

4. How to Select the Right DJ-S Model

Step 1: Determine Your Torque Requirement

• Calculate the torque your application requires.

• Select a model with rated torque ≥ 1.5× your requirement.

• DJ-S series covers 20–4800 N·m.

Step 2: Match Shaft Diameters

• Measure your shaft diameters.

• Select a model with a bore range that accommodates your shafts.

• H7 bore tolerance is recommended for precision fit.

Step 3: Evaluate Misalignment

• Determine the expected angular, radial, and axial misalignment.

• DJ-S series accommodates angular up to 3.4° and radial up to 2.5 mm.

Step 4: Consider Speed Requirements

• Verify the coupling’s maximum speed exceeds your operating speed.

• DJ-S series offers speeds up to 19000 RPM.

Step 5: Consider Space Constraints

• Measure available space for the coupling (outer diameter and length).

• DJ-S series offers compact sizes from 40 mm OD.

Step 6: Consider Keyway Requirements

• For applications requiring keyways, specify when ordering.

Step 7: Select Material

• 45# steel – high strength, standard industrial applications.

• Aluminum alloy – lightweight, low inertia, high-speed applications.

5. Applications Where DJ-S Couplings Excel

6. Real‑World Example – Machine Tool Upgrade

A CNC machine tool manufacturer was experiencing positioning errors and vibration on their main spindle drives. The existing coupling had backlash and could not compensate for the thermal expansion-induced misalignment.

They switched to Apex Coupling DJ-S double star elastic coupling (45# steel, dual elastomer, zero backlash). Results:

• Position errors eliminated – zero backlash

• Vibration reduced – dual elastomer design absorbed shocks

• Misalignment accommodated – superior deviation compensation

• Maintenance eliminated – no lubrication required

• Accuracy improved – H7 precision bore

7. Installation & Maintenance Tips

1. Clean shafts – Remove oil, grease, and debris before installation.

2. Check alignment – Even with misalignment compensation, keep within recommended limits.

3. Axial plug-in installation – Slide the elastomers between the hubs – no special tools required.

4. No lubrication required – Coupling is maintenance-free.

5. Periodic inspection – Check elastomer condition periodically.

6. Replace elastomers – When worn, replace without moving hubs.

8. Selection Checklist

• □ 

  Type: DJ-S – double star elastic coupling

• □ 

  Structure: Dual elastomer – superior misalignment compensation

• □ 

  Material: 45# steel or aluminum alloy

• □ 

  Backlash: Zero backlash – precision applications

• □ 

  Bore: H7 tolerance – match your shaft diameters

• □ 

  Torque: 20–4800 N·m – ensure it exceeds your requirement

• □ 

  Speed: Up to 19000 RPM – match your motor speed

• □ 

  Misalignment: Angular, radial, axial – verify capacity

• □ 

  Maintenance: Maintenance-free – no lubrication

• □ 

  Application: Machine tools, lifting platforms, servo motors, compressors

9. Conclusion

The DJ-S double star elastic coupling from Apex Coupling offers the perfect combination of zero backlash, superior misalignment compensation, and maintenance-free operation for demanding industrial applications. With dual elastomer design, 45# steel or aluminum construction, and OEM customization, it is the ideal solution for machine tool spindles, lifting platforms, servo motors, and general industrial machinery.

👉 Need a double star elastic coupling for your application? Contact us with your model, bore, and torque requirements.