Bellows couplings with shrink disc locking are among the most precision-engineered flexible couplings available for servo motor, stepper motor, resolver, and CNC applications. With zero backlash, high torsional rigidity, and corrosion-resistant stainless steel bellows, they are the preferred choice for demanding motion control systems.

The DLK series from Apex Coupling combines a stainless steel bellows with a shrink disc locking system for secure, keyless shaft-to-hub connection. This guide explains how bellows couplings work, the advantages of shrink disc locking, and how to select the right model for your application.

1. What Is a Bellows Coupling with Shrink Disc?

A bellows coupling with shrink disc consists of:

• A stainless steel bellows – flexible, corrosion-resistant element that transmits torque while compensating for misalignment

• Two hubs – precision-machined from S45C steel with H7 bore

• A shrink disc (shrink disc) locking system – keyless friction-lock connection for secure shaft-to-hub attachment

The bellows flexes to accommodate radial, angular, and axial misalignment while maintaining constant velocity rotation in both directions. The shrink disc provides a secure, backlash-free connection without keyways.

💡 Bellows couplings are widely regarded as the ideal solution for servo drives due to their zero backlash, high torsional stiffness, and low moment of inertia [1†L24-L26].

2. Why Bellows Couplings Are Ideal for Servo Motors & Resolvers

Bellows couplings meet the critical requirements of servo motor and resolver applications:

✅ Metal bellows couplings have proven themselves in numerous servo drives as an excellent choice [1†L24-L26].

3. Shrink Disc vs Traditional Keyway – Why Choose Keyless Locking?

✅ The shrink disc locking system eliminates keyways, stress concentrations, and backlash – providing superior performance for precision applications.

4. Stainless Steel Bellows – Corrosion Resistance & Flexibility

The DLK series features a stainless steel bellows that offers several advantages:

• Corrosion resistance – Withstands moisture, chemicals, and harsh environments – ideal for food, chemical, and outdoor applications

• Excellent flexibility – Compensates for radial, angular, and axial misalignment

• Constant velocity – Identical clockwise and counterclockwise rotation

• High fatigue resistance – Long service life under cyclic loads

• Suitable for reversing applications – Performs equally well in both directions

💡 The stainless steel bellows material is suitable for positive and negative rotation with excellent corrosion resistance.

5. Zero Backlash – Why It Matters for Servo Motors

Backlash (rotational clearance) in a coupling causes:

• Position errors – Inaccurate feedback in servo systems

• Reduced accuracy – Poor system performance

• Control instability – Oscillations in motion control

• Reduced repeatability – Inconsistent positioning

✅ A zero backlash coupling ensures accurate positioning – every time. Along with high torsional stiffness, zero backlash allows the coupling to maintain the same angular relationship between input and output shafts without lost motion [0†L5-L8].

6. Key Specifications to Consider

When selecting a bellows coupling with shrink disc, evaluate these parameters:

7. Applications Where Bellows Couplings Excel

8. Real‑World Example – CNC Machine Upgrade

A CNC machine manufacturer was experiencing positioning errors on a high-speed machining center due to backlash in their existing coupling. The coupling also required frequent lubrication and was susceptible to corrosion from coolant.

They switched to Apex Coupling DLK bellows coupling with shrink disc (stainless steel bellows, shrink disc locking, zero backlash). Results:

• Positioning accuracy improved – backlash eliminated

• Corrosion eliminated – stainless steel bellows withstood coolant exposure

• Maintenance eliminated – no lubrication required

• Service life extended – stainless steel bellows withstood millions of cycles

• Installation simplified – shrink disc locking, no keyway fitting

9. 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. Slide coupling onto shafts – Position at desired axial location

4. Tighten shrink disc screws evenly – Use a torque wrench in a star pattern to specified torque

5. Check concentricity – Verify alignment after tightening

6. No lubrication required – Bellows coupling is maintenance-free

7. For removal – Use removal thread holes – no pullers required

8. Cross-tighten – Perform tightening of fastening screws crosswise to avoid distortion of the coupling hubs [1†L31-L33]

10. Selection Checklist

• Type: DLK – bellows coupling with shrink disc locking

• Model: DLK14-40 to DLK14-200 – select based on torque and bore requirements

• Material: Stainless steel bellows – corrosion-resistant

• Locking: Shrink disc – keyless, zero backlash

• Backlash: Zero backlash – precision positioning

• Bore: H7/H8 tolerance – match your shaft diameters

• Torque: 13–200 N·m rated – ensure it exceeds your requirement

• Speed: 2000–8000 RPM – match your motor speed

• Misalignment: Radial, angular, axial – verify capacity

• Maintenance: Maintenance-free – no lubrication

11. Conclusion

The DLK stainless steel bellows coupling with shrink disc from Apex Coupling offers the perfect combination of zero backlash, high torsional rigidity, corrosion resistance, and maintenance-free operation for servo motor, stepper motor, resolver, and CNC applications. With stainless steel bellows, shrink disc locking, H7 bore precision, and OEM customization, it delivers reliable, long-lasting performance in demanding industrial environments.

👉 Need a bellows coupling for your precision application? Contact us with your model size, bore, and torque requirements.