Bellows Coupling with Shrink Disc vs Clamp Type – Which Connection Is Better for Your CNC Machine?

Bellows couplings are essential for precision power transmission in CNC machines, servo motors, and high-accuracy automation. But one critical decision is the shaft connection method – shrink disc or clamp type?

This guide compares both connection methods, explains the advantages of the DRZ stainless steel bellows coupling with shrink disc, and helps you choose the right solution for your CNC application.

1. Quick Comparison: Shrink Disc vs Clamp Type

2. What Is a Shrink Disc Connection?

A shrink disc (shrink disc / locking assembly) is a mechanical locking device that creates a friction-based connection between a shaft and a hub. It consists of:

• An outer ring with tapered surfaces

• An inner ring that fits over the shaft

• Screws that, when tightened, compress the inner ring onto the shaft

✅ The shrink disc provides a secure, backlash-free connection that can handle high torque loads without keyways.

3. Why Choose a Shrink Disc for CNC Applications?

Shrink disc connections offer several advantages for CNC machine tools:

• High clamping force – Handles high torque loads without slipping

• Zero backlash – No rotational clearance – critical for precision positioning

• No keyway required – Eliminates stress concentrations and backlash from keyway clearance

• Easy installation and removal – No special tools required

• Reusable – Can be disassembled and reassembled multiple times

• Even pressure distribution – No shaft damage or deformation

4. Why Stainless Steel? – Corrosion Resistance and Durability

The DRZ series features full stainless steel construction:

✅ Stainless steel is the material of choice for CNC machines in harsh or clean environments.

5. Laser Welding – Ensuring Zero Backlash and Straightness

The DRZ series uses laser welding to join the bellows to the hubs. Benefits include:

• Superior strength – Laser welding creates a strong, durable joint

• Perfect straightness – Welded while mounted on a common shaft to guarantee alignment

• Zero backlash – No rotational clearance

• Reliable performance – Consistent torque transmission

6. Misalignment Compensation – Protecting Your CNC Machine

The bellows structure compensates for three types of misalignment:

By absorbing these deviations, the coupling reduces stress on bearings, seals, and other components – extending CNC machine life.

7. Applications – Where DRZ Bellows Couplings Excel

8. Model Designation – Understanding DRZ Codes

DRZ – □□ x □□ – □□ x □□

Keyway Option: Add “K” after the shaft diameter for keyway.

• Example: DRZ-55×75-10k x 11k – both bores with keyways

9. Real‑World Example – CNC Milling Machine Upgrade

A CNC milling machine manufacturer was experiencing positioning errors due to backlash in their existing clamp-type bellows couplings. The backlash caused poor surface finish and reduced machining accuracy.

They switched to Apex Coupling DRZ stainless steel bellows couplings with shrink disc (laser welded, zero backlash, H7 bore). Results:

• Positioning accuracy improved – backlash eliminated

• Surface finish enhanced – consistent machining quality

• Corrosion resistance – stainless steel withstood coolant exposure

• Easy installation – shrink disc connection simplified assembly

10. Installation & Maintenance Tips

1. Clean shaft and bore – Remove oil, grease, and debris

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

3. Tighten shrink disc screws evenly – Use a torque wrench to specification (star pattern)

4. No lubrication required – Dry connection for maximum friction

5. Inspect periodically – Check for wear or damage

6. Retighten after first operating hours – Normal bedding-in process

11. Selection Checklist

• Connection type: Shrink disc (DRZ) for high torque, zero backlash, easy installation

• Material: Stainless steel for corrosion resistance and durability

• Joining method: Laser welded for strength and straightness

• Bore size: Send us your shaft diameters – we will match

• Keyway: Add “K” if required

• Application: CNC machine, servo motor, or general industrial

12. Conclusion

The DRZ stainless steel bellows coupling with shrink disc from Apex Coupling offers the perfect combination of zero backlash performance, corrosion resistance, and easy installation for CNC machine tools. With laser welded construction, full stainless steel material, and shrink disc connection, it delivers reliable, high-precision power transmission in demanding applications.

👉 Need a bellows coupling with shrink disc for your CNC machine? Contact us with your shaft diameters and requirements.